The Joyfit Resistance Toning Tube is made with 100% Natural Latex which makes it highly strong and elastic. The metal hooks at the end of the tube help it attach efficiently to the handles. You can stack multiple resistance tubes together and take your resistance training up a notch. The resistance tubes come with 5 resistance levels,color-coded as Yellow (10 lbs),Blue (20 lbs),Green (30 lbs),Black (40 lbs),Red (50 lbs). Whether you are a beginner or advanced,you can always find the right tension level for your workouts. You can use the resistance tubes to train your upper body including your legs,chest,shoulders,arms,and back with a number of resistance tube exercises such as Bicep Curls,bent-over row,chest press,Hamstring Curls,and Resistance Squats,etc.