Hello there. Very good question. Did you use our tights finder on CW-X.com? and you did not get the answers you were looking for? Anyhow, the CW-X Stabilyx tight is our best Stability tight that supports Knees, Lower back, Hips, and Quads and is best for high impact activities that have a lot of movement from side to side. For example Trail running, Skiing, Hiking, etc. The Pro tight works best for constant motion activities that are not as high impact. For example Road running, Nordic skiing, etc. The pro tight does not have the knee support like in the Stabilyx, but it does offer more Hamstring support. Versatx is a softer support system that only focuses on Hips and lower abs. The performx tight is new and focuses on support through the IT band specifically. it only offers medial and lateral knee support (just on the sides of the knee). The Stabilyx tight is the best all around tight if you plan to use it for a variety of activities as a base layer or an outer layer. Hope this helps answer your question.