Don't buy the knock-offs! They are not nearly as effective as the real McCoy. I own a black pair and white pair. The best place to find authentic ones are at an Army/military surplus store. I use them to hunt and fish. They have a valve stem attached to allow air in and out of the air bladder that some what surrounds your foot. You will allways keep the valve closed to keep moisture from rotting the insides. Tha valve is for the pilots that use them. The altitude contracts the boots and air must be let in, at least that is my understanding about the valve. I fish in double digits below zero with these and have never gotten cold feet yet. If they get submerged, you just pull off the boot, wipe it dry, and put back on with fresh
socks. Definately buy a pair if youhave a chance.