Depending on what exactly is in them and how full you fill them, they're more like a bag of beans or egg noodles than a bag of flour - flexible. You can also take that into account when storing. I know mine are going into buckets, so I sit them on a counter, squish them so they sit upright, and fill in a little more of a brick kind of shape. In round buckets, you still get some extra space inside, but a couple fit "upright" and a couple go flat, then a couple sit upright again but rotated the way you would Jenga bricks.

You can store Mylar bags in anything you want - they're what's preventing oxididation and light. The 5- and 6-gal food-grade buckets are just popular because it's a manageable size/weight, it's relatively to short-term water proof, the lids are relatively easy to get on and off even without gamma twists, and many/most stack well.
I also have Mylar or other glass & plastic sealed packages in barrels, aluminum trash cans, Big Boy super-thick trash can with wheels, a future rain barrel, washed kitty litter buckets (requires something between layers to stack, but so do regular buckets in some cases), Rubbermaid storage totes of 2 main sizes, cardboard boxes, and milk crates.
The Rubbermaid won't seal against water without a lot of help, and neither will the trash cans. I use an extra layer of plastic (tarps, 1 tent) in trash cans even though the contents are sealed against the plastic leaching. The cardboard and milk crates are vulnerable to insects. Too much weight on Mylar with air pockets can pop bags or a the super-duper crazy-heavy mil-level Mylar can poke holes in 5 mil and 7 mil bags if the corners aren't folded over.

If you really end up having a problem, use a pot/canner the same diameter as the bucket to hold the bags while you fill them. Sit two in there at once, stick the O2 absorbers in a canning jar and set the lid on it (they'll suck it down), fill the bags, stick the first O2 absorber in the first bag and sit the lid on the canning jar again, seal the bag, pop the jar and stick the second O2 absorber in there, seal that bag, either progress through the line of bags & pots or stick them in the bucket and arrange the next pair. You can also use 2L soda bottles with the funnel neck cut off or pitchers about the same size as molds.
It's not usually a problem, though.

If you really have heartburn with the amount of space you have left, go to the dollar store and buy salt in cartons, stick it in Ziploc, and buy the shaker tubs of dehydrated onions or garlic, lemon pepper, seasoning salt, garlic or onion powder, or any non-green spice. They'll last about the same amount of time.
You could also refill small plastic shakers with sugar or seal sugar in small Ziploc bags, stick in small containers of pure honey or maple syrup (super long storage life), or use the space either for small pick-me-up books or activities, hankies, a new pair of socks or underwear here or there, candles, bar soap that's sealed like the devil - any of the heat-independent nonperishables that will fit in your gaps without poking holes in Mylar.

If you really end up having a problem, use a pot/canner the same diameter as the bucket to hold the bags while you fill them. Sit two in there at once, stick the O2 absorbers in a canning jar and set the lid on it (they'll suck it down), fill the bags, stick the first O2 absorber in the first bag and sit the lid on the canning jar again, seal the bag, pop the jar and stick the second O2 absorber in there, seal that bag, either progress through the line of bags & pots or stick them in the bucket and arrange the next pair. You can also use 2L soda bottles with the funnel neck cut off or pitchers about the same size as molds.
It's not usually a problem, though.

Thanks, that is a great idea to fill 2 side by side in a pot to fill them in pairs. I suppose a piece of cardboard could be cut to go between layers to prevent poking holes
into adjacent layers.

MrsPrep, do you find the 5 or 6 gallon pail works better , they are not much different in price, and I will be buying some, so not sure if I should stick with 6 gallon
or stick with 5 gallon.

And what size 1 gallon mylar are you getting ? are they 10 x 16 ?

Thanks, that is a great idea to fill 2 side by side in a pot to fill them in pairs. I suppose a piece of cardboard could be cut to go between layers to prevent poking holes into adjacent layers.

It's not usually a problem unless you get the 6-7.5 mil that's designed to stand up on one end and are using a 4.5-5 mil flat on top of it. Most of the time, just folding it over at the seal line so the "top" isn't standing up is sufficient, but a piece of cardboard would do the trick, absolutely. Good idea.

do you find the 5 or 6 gallon pail works better , they are not much different in price, and I will be buying some, so not sure if I should stick with 6 gallon
or stick with 5 gallon.

Whatever is free, man. You heard the bit about kitty litter boxes, right? You might want to crunch some numbers and consider what you're packing to figure the weight it'll be and then:
-if you're going to want to use it for water ever (~8# per gal)
-if you're stacking, the height you have available + a board height from free pallets or free bookcases you take apart or plywood sheet between layers
-the height you can comfortably lift a 40-65# container
(in some spaces, 3 levels of 5-gal or 4.5 gal buckets might fit, but only 2 6 gal, especially with a .75-1" board layer between each; that's 13.5-15 gal of storage per column for the first 2 sizes, only 12 if I can't wedge a 3rd 6 gal in there, but it's 18 gal if 3 6-gal buckets fit, and that may be more economical, space-wise. However, above the stack you could go with flats of canning jars or commercial cans or Rubbermaid tote(s) and caulk+duct tape for sealing.)

If you're working in pairs, 6 gal bags go in more evenly. My bags are usually a hair on the "just in case" size because I end up with about 1-2.5" of "cutting" space above food to allow me to twist-tie it shut (it's probably more like .5-1" for 1-gal bags) and below a 1" band of melted-together seal, so I usually get 6 into a 5-gal anyway, but it's not a full 5 gal of food - it's probably more like 4.5-4.75 gallons.

And what size 1 gallon mylar are you getting ? are they 10 x 16 ?

Whatever's cheapest - the 5-7 mil is more important to me than exact size, and I factor in total volume and just buy 1, 1.5, 2, or 2.5 gal bags that work out to be least expensive.
The last ones I bought are 12x18 and 14x20. They're about 1.25-1.5 gal, so 10x16 sounds right.

I am seeing various sizes listed as 1 gallon mylar bag, such as
10 x 16 , or 10x 14...

Watch the 10x14" bags.

A lot of them are kind of nice because they have that stand-up panel and the zip closure, but I've found that they don't have as much extra space at the top for sealing. I'm a spaz and I really, really want a wide band sealed. Plus, it's a whole lot easier and labor is more economical if you've got wiggle room at the top and you're not fighting to hit this exact 1/2" or 1/4" to avoid melting the little plastic zippy do.

Edit: Added note
Not all the 10x14's may be like the style shown above (and I'm not usually willing to pay for that style), but a lot of the 10x14's that I see are. Just something to be aware of.

I am not wanting the ZIPPER tops either. I found some 10x16 on Amazon with the exact # of O2 absorbers that might
work for me for a first try.

I think another useful size would be a 8 x 9 size , but the ones I am seeing are either zipper at the top,
or a thin mil of 2.5.

I also see alot of 3.5 mil bags offered. I would think with those you would HAVE to use in a bucket.

Not sure but perhaps the 5mil bags don't have to be in buckets to keep light out ? I get alot of buckets from pool chemicals which I wash in the pool water
but I use them for other things, such as gathering kindling and storing. Kitty litter containers I used to get
but I have no cat, but I have used them for growing things in. I like how they are square. LOL

HomeDepo and places have buckets , and perhaps mason jars could be put inside them. But these
are 5 gallon, and the pool chemicals are 3.5 gallon.

I think another useful size would be a 8 x 9 size , but the ones I am seeing are either zipper at the top, or a thin mil of 2.5.

I really hope I'm not sending you on another wild goose chase with these:
Watch the package strength/thickness, but if there's a size you want and you're not finding it through LDS, Amazon, eBay, etc., one of these should have it:
http://www.sorbentsystems.com/mylar.html - the main pricing/size chart starts about 1/4-1/3 of the way down the page
https://www.usaemergencysupply.com/emergency_supplies/mylar_food_storage_bags.htm#.U2F8JldkUh0 - half gallon but no quarts, at the bottom of the page
http://www.mylarbagsdirect.com/300xx.html - 5 mil quart bags + 300cc O2 absorbers
http://www.lexingtoncontainercompany.com/Mylar-Bags.html - You have to call for ordering to let them do up shipping

I also see alot of 3.5 mil bags offered. I would think with those you would HAVE to use in a bucket.

Sometimes it's not only light, but durability of the bag itself. Think about cellophane on store shelves. Heavy plastic egg noodle and spaghetti bags can take a lot of abuse, whereas if they're not in something, bags of beans sitting in a stack on a wire shelf can exert so much pressure they end up "squeezing" a hole in the bag. With some thicknesses, what's going in it starts to play a factor (sharp points on cubed carrots, noodles, even larger beans and arranging for those gaps).

Not sure but perhaps the 5mil bags don't have to be in buckets to keep light out ?

We go back and forth over this one, and I'm pretty wishy-washy with it. I do look at some of the storage companies, though. Mountain House sells small 1-2-4 person pouches, a thicker group pouch, and cans. For the sausage gravy, the 1-4 person camping meals have a 7 year shelf life, the larger pouch (also thicker) has 10 years, and the cans have 20 or 25 years. I see the same thing with some others. Inside the bucket, two different companies say their pouches will last 15-20 years. They say the pouches on their own will last 5-10 years.

I don't know if it's a case of light degrading the quality of the Mylar (like plastic sheeting and PVC left outside and exposed will eventually start breaking down), or if the slowing of oxidation from the bucket (not perfect, but takes longer in a bucket than in a brown paper bag) contributes to the shelf life.
There's also the pest factor, which is where I end up beaten about the head, but I don't currently have pests and I usually have pest-repelling herbs and some chems, and I have small suet cages and similar I can arrange with seed to catch mice without endangering the kitty. The stuff that sits in cardboard and in milk crates is typically stuff I'll be rotating through fastest and usually home-dehydrated stuff, stuff with 2-5 year shelf lives at my temperature, or stuff that could handle exposure even though it would turn into a brick (sugar, salt).
So absolutely, 5-7 mil keeps out light, but you may still be looking at a reduction in storage life and you're vulnerable to pests.

HomeDepo and places have buckets ..... But these are 5 gallon, and the pool chemicals are 3.5 gallon.

3.5 is a nice size, personally. I can haul it even when achy and even when it's muddy or snowy, whether it's full of kitty litter or water or seed/grain.

Check around the local bakeries and delis, inside supermarkets/grocers as well as regular ones along the road. Also try BBQ places for their pickles and caterers - they sometimes get ingredients in them still. A lot of places are now getting stuff JIT shipping, and it's now being shipping in plastic bags inside cardboard boxes (bastards, but also better for the environment). You can also contact local pet stores or animal shelters, to see if they get either feed or litter in buckets. Sometimes you might end up paying a small fee, but usually not nearly what my Home Depot and Lowes want for a bucket and not what I would pay to order just 5, 10 or 20 food-grade buckets.

If you're comfortable with the pool buckets, you can try to contact cleaners/maintenance companies around you to see if they have spares, and since you already plant in buckets (me, too) you can offer that excuse, or explain how you're turning them into sub-irrigated planters/buckets.

HomeDepo and places have buckets and perhaps mason jars could be put inside them

I usually just grab free wine/liquor boxes from a store to keep canning jars in, for the ones purchased since they stopped selling flats that close over the top completely. I can cut them down quickly, add an "I" of duct tape to the bottom for added security, and they stand up to time well. I use the same types of boxes to make 20oz and 2L bottles stackable as well, although I'll stick them in the taller kitty litter buckets, upending the second layer for less space loss. A bunch of canning jars are loud and HEAVY. The smaller buckets would work better for them, I'd think, if you really want to go that road.

I only use the pool buckets for outside things. But there are alot of things to use buckets for.

And I also have noticed how annoying it is to buy a new flat of mason jars, and there is only the bottom tray now,:(

I wonder if we order them from walmart, they ship free, and maybe they will come in a proper box.

LOL

I wonder if we order them from walmart, they ship free, and maybe they will come in a proper box.

Call and check first. My Wal-Mart carries the Ball jars with barely enough cardboard to hit the rims on pints and not even all the way up to the slanting necks on quarts. Sometimes they have the full boxes for half-gallon jars.

Let me know if you check and they'll ship the full-coverage boxes, if you don't mind. I can always come up with a $45 bill at Wal-Mart. 🙂
I've found them here and there, used or new, but either shipping is incredible, the in-store places are small and have high overhead and possibly think those lids and rims are gold, or the boxes are so beat up from time and water and sheds that I have to replace them anyway.

Well I am guessing it will be an OVER box on the new lower tray covered in plastic ..
but of decent cardboard for shipping. It is just a matter of how much bigger that box is or if it is a decent fit,
or if it is a loose fit filled with packing stuff.

I looked on Walmart, and at the moment in Canada the one I would buy is out of stock. They have more canning
stock than couple months ago, so they are probably restocking for the summer season still.

What do you think of the BLUE mason jars ?

What do you think of the BLUE mason jars ?

I'm not against it. Old timers used to think it made food last longer. I don't know if they're actually effective at that, really.