This mock neck thermal combines the soft, light feel and strength of microfiber polyester with an interlock construction to give you warmth without weight and freedom of movement. The interlock knitting of this men's traditional roll down t-neck base layer top is like having a double layer since the two sides are technically knitted the same (face out with the backs "interlocked" together) allowing more space to trap air and more stretch than a flat surfaced fabric. Order this men's lightweight base layer today!