I bought this set of bands to work on rehabbing my knee outside of the gym. This type of product is certainly convenient to use and offers a fair amount of resistance for my purposes. However, for those intent on building gobs of muscle, weights are of course ideal. I found that I needed some time to adjust to the feel of these bands. While the manual indicates some type of pound rating it doesn't feel accurate. The nominal rating of weak to strong is a better way to judge the resistance of each band. I chose a familiar exercise that would allow me to work through a range of bands. I knew what I  could lift with weights and compared that sensation to the band with a similar resistance. From there I could start to estimate which bands i might start with  for other exercises. The kit is nicely put together with a wide range of bands and extra straps for doors and ankles. The carrying bag holds everything without being cramped and is well suited for travelling. As another reviewer noted, the bands are rubber and are subject to wear. It behooves the user to inspect them regularly before use.