A few years ago I tore a tendon in my shoulder. I was in physical Therapy for 6 months. about half of my exercises were resistance bands. They were basically strips of latex in different colors for various strengths. They did work and I trained my muscles to be able to function without that one end tendon. Now I wanted to get some new ones to continue exercising mainly in the winter as I am very active the rest of the year. My trainer form blue cross showed me some models out there that were endorsed by Blue Cross. I noticed he used these from Black Mountain that were not on the list. He explained that he was on a budget and the latex tubes are all fairly equal. I did some research and they all last about a year if used every other day. I bought them and they are so much better than I was expecting.