I picked up a package of those a couple years ago and they are nice heavy material, don't know what weight but they are sturdy, none of mine have failed and I've used some multiple times. They came in a package of 30 or 50 and less than $3. Even have a place in white on the side of each bag to write what's inside or date etc. Great for anything that might leak too, like batteries or tubs of ointments. Riteaid also sells them.