Resistance Tubes offer a safe alternative to Latex tubing by using a multi-stranded rubber core with a protective nylon sleeve, which prevents the possibility of sudden tube failure that can occur with latex tubing. The rubber offers natural and progressive resistance and avoids the possibility of latex allergies. Available in 3 strengths with comfortable integral foam covered handles The resistance level is marked on the handles to make identification easier when using in a class or studio environment. These tubes do not come with a user guide. Max tube stretch 3 x original length.