The Evolution 20 is the next “Evolution” in the resistance activated releases. The Evolution 20 no longer requires a spring change like the “plus” models with the ITS system. One spring under a screw is the only adjustment needed with a weight range from 8 pounds all the way up to 40 pounds of holding weight. This system also has the advantage of a much more precise micro adjustment of weight, as well as improved consistency. Carter Evolution 20 3 Finger Release RBEV5135