It's a pretty simple principle: You sit on rocks and tundra, you get a cold butt. I decided to remedy that this year and make my own pad. I'm a pipe insulator by trade, so I found a couple old pieces of foam insulation and just glued them together. It's quite a bit thicker than most pads you can buy, weighs practically nothing, and is very inexpensive. The insulation not only keeps you dry and off sharp rocks, but it also helps warm your butt during long hours of sitting and glassing.