MENS LONG UNDERWEAR WITH FLY Long Johns 200 Long johns are made of circular knit fabric, and have no lengthwise seams. A gusset in the back ensures optimal comfort. Cuffs are knitted in. 60% Merino Wool 25% Polyester 13% Polyamide 2% Elastane Weight M: 174g 200 g/m2 undergarments are designed to be worn directly against the skin as a moisture wicking base layer. This weight undergarment is ideal at temperatures ranging from -4 F to 50 F degrees depending on the activity level.