What's up with these tall grow bags?

I ordered a few 20 gallon grow bags and didn't realize they were so tall? Mine measure out at 15" wide x 13.5" deep X 36" tall. When I calculate it out compared to my 5 gallon pots they can hold 7x what the 5 gal pots can hold. I checked the package to be sure they were 20 gallon and yep, it says 20 gallon grow bags followed by the dimensions. So I guess these are really 35 gallon grow bags if they were filled the the brim but that would be just plain stupid right? I'm thinking 1 1/3 bag of some FF ocean forest should be about 20 gallons and put me somewhere just above the halfway mark. So anyone know why the heck these things are so tall?

Well they make the smaller ones, like 1-5 gallon types, taller and skinny so you can get more in a given space when growing indoors under lights. As for why yours are so tall I have no idea. I can see leaving a little room there at the top, but 15 extra gallons is a lot of space. You sure you are doing your calculations right?

I'm pretty sure since my round 5 gal pots are 10" wide and 12" tall, so 3.142 x 25 x 12 = 942.6 cu inch per 5 gallon pot. The bags would be 13.5 x 15 x 36 = 7290 cu inch. so that would put the bags at 7290/942.6= 7.73 7.73 x 5gal = 38.6 gallons. they look like I'd have no problem filling it up with two 1.5 cu ft bags of soil and still have a tad bit of room. I guess since I'm only going to fill these about 1/2 way I could scrunch the top of the bag around the stem of the plant to help keep the root ball moist and cool, kind of like how mulch works.

Is it the cloth type? Most of the time the top few inches get folded down to dubble it's layers. This acts as a stiffening ring.

1 1/3 =133% one bag plus a third of a bag.
1/3= 33% a third of a bag

Warlock1369 said:

Is it the cloth type? Most of the time the top few inches get folded down to dubble it's layers. This acts as a stiffening ring.

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These ones are plastic, white on the outside and black on the inside. I guess I can fold the extra down and make it stiffer