These tights, as well as the Stabilyx model, are some of the best -if not THE best- compression running tights I have purchased.  I have tried different brands, but CW-X is really at another level.  The design in the Pro tights gives amazing support to quads and hamstrings, reducing the impact of the long runs.  Personally I use them for the long runs, and for racing.  The Stabilyx model offers more support for the knees, and ITB.  It's been 4 years since I have been using CW-X and I'm a very happy customer.  If you choose to buy the Revolution tight though, be careful because that model runs smaller than the rest.  I am XS in the Pro, Stabilyx and Ventilator, and M in the Revolution.