Four-way stretch thermal under-shorts for an extra layer of warmth during cold weather workouts. This is the winter layer you didn't know you were missing. MidZero is a full stretch wicking midweight base layer with a fleeced inside for amazing comfort Firewall 180 fabric on rear panel for wind and water protection Flat seams for increased comfort 1 1/4" signature moisture wicking comfort elastic waistband Fabric: MidZero (87% Polyester 13% Spandex