They are standard rectangular bales. I have just measured the space that one takes up in the van and I make them 4' long by about 18- 20" (or a bit more) square(ish).
I usually decant a bale by the 'slabs' that they fall apart into and these fill 4-5 plastic bags that used to be the big snowflake sawdust bales, probably a bit bigger than dustbin liners.
I can get a more accurate measurement later in the week if you need it, but this sounds like better value if you can get it collected and can store it.
PS. I've just noticed the size you quoted on the previous post. It looks like the small bales are just a half of a standard bale.