I bought these for winter cycling.I bought 4 pairs to start, and followed the directions.For the first pair, I gave them 30 minutes to warm up, then i put them in my gloves (directly on the skin) and went for a ride in 39-degree weather. After the first minute, they got cold and I couldn't feel them. I thought this might be due to fact that my gloves are windproof, so i tried a second pair.The second pair - same thing - 30 minutes to warm up.This time i tried them in a pair of thin liner gloves, so they'd have plenty of oxygen. They're warm (not hot) indoors, but these were negligible once i got outside.Both pairs have a 2015 expiration date.Bottom line - i'm going to try another brand.