Does exactly what the description says.This flimsy plastic bag is really worthless. It made our mattress foundation more difficult to transport and any small amount of scooting along the floor made holes in it. We ended up wrapping the whole thing with cellophane to protect it.Zipper broke when pulled thru cheap materialThis mattress bag is pretty thick and sturdy. Your mattress will be protected from dirt and most insects but I'm not sure how waterproof it is. I knocked off one star because I have difficulty putting it on the mattress alone. But I would say this is great for moving.used this when I moved my son and then again in a month when we moved my daughter. it worked very well and protected the mattress from dirt and scuffing.The clear plastic bag slides over the end of the mattress. The bag is so large that it easily slips on. The bag does not have a closure so it did slide down a few times. The bag was used to to move a queen size memory foam matress down a narrow flight of stairs and into the back of a van. The slipperyness of the plastic bag material did make it challenging to keep a grip on the matress through the bag because the matress does.not have handles but the bag got the job done and did not rip. Great value for this waterproof matress protector.The package says it is for queen but maybe I got the incorrect size? I laid it flat on top of the mattress and didn't even bother trying as it barely reached end to end width wise. It's odd given other good reviews.No matter though, I can use it for something smaller, perhaps the futon. The thickness of the plastic is okay. I got another bag since this didn't fit at 4mil and I think it's better if using when moving.Old mattress requires proper disposal and this bag fit the bill,thick mil plastic made it easy to fit