The Jolly Gear resistance bands are made of a durable, heavy-duty rubber and are colour coded for specific resistances from light (red) to XXX-Heavy (orange). The bands fold up to a compact size small enough to fit in any gym bag and the X-Heavy green weighs less than 400g so are ultra-portable. You can take them to the gym or are perfect for home use negating the need for expensive and bulky equipment. You can do a myriad of exercises with the bands including squats, leg curls, push-ups, bicep curls and work every possible muscle group.The advantage of using resistance bands over machines is the ability to use your own bodyweight, plus your desired strength of the band, which gives you a functional workout with a full range of motion, at your desired resistance. Machines, however, can limit your range of motion and for some, can cause injury or even agitate old injuries. Resistance bands are a superb addition to your fitness program and are now highly recommended for rehabilitation workouts post injury and good for maintenance workouts of past injuries, or for those with general body wear and tear issues, whereas machines often aggravate the problem. Variety is also important to keep your workouts fresh and to get over workout plateaus. Highly Recommended!