10" and 15" long loop is equivalent to 20" and 30" of flat band cut and tied in a knot. Loop is 3" wide. Convenient pre-formed loop is made of high quality latex exercise band. Loops arrive ready-to-use, you do not have to cut and tie it before performing exercises! 10" long loop is specially sized for upper body exercises while the 15" long loop is specially sized for lower body exercises.