I didn't test them, I ordered another Marmot pair and liked them better. The thing I didn't like about these was that the glove liner was tacked inside, so your hand would be unprotected to remove it from the mitten. Also, a large was too big. I measure 3.5 on one scale and a 7 on the other kind. I think I would have gotten a m or s for this . The Burton Gore-Tex mitten was delightful. I went outside with one of each on my hand and the BGT hand started feeling warm within seconds. But I haven't been skiing in them yet.
For those below zero days your fingers will be in paradise. Enjoy the riding longer with the insulator mitt. Thermacore is developed for those who need superior warmth. To top it off it comes with heater vent pockets for hand warmers. One free pair included. Wooo hoooo let it storm !
Great mittens! Very warm and waterproof. I have not used the heater, but I think it would be even hot! I recommend!