I have this kit and I love them! For P90X you need to change up your weights from time to time and also increase your resistance as you build up your strength. I have a small apartment and having a whole set of dumbbells is totally out of the question. I keep these little bands in a storage bin with my workout DVD's and booklets and shove it under my bed. These bands are pretty durable. The only part of using the bands that can get tricky is when you have to loop the band and step on it for certain exercises, like over the head presses, or curls. You have to secure it under your foot and make sure the tension is right. But you will get the hang of it quickly if you have a regular workout routine. On tip I would give people who are thinking of getting these bands is to get extra handles for all of the bands. It's not that hard to switch the handles, but if you need something heavier while you are doing the workout, it's better to have one ready rather than having to switch the handles. There are 10 bands and three sets of handles. The extra handles are less than 5 dollars a set, but still I really wish that they just came with all the handles you need.