I use them for 1/2" & 3/4". They are not for sked 80. I live in the desert, we just lay the pipe in the sun for a few minutes,then bend it over out knee. A little overbend helps because it does return slightly. Helps to hold it in it's bent position for a minute before letting go. I love it, it's fast and easy. Never gets stuck inside the pipe anymore after we attached a length of twine!
Don't know how good it would work in the cold, we seldom work in temps below 60.
