I personally don't think it CANT create traction once it's past your normal erection length in the pump, at this point it is also pulling it; causing traction. I believe the reasons people's length gains by pumps aren't as much is because pumping is usually a 15-40 minute things vs stretchers are usually in hours, so the gains are there but you won't have it the same amount due to the time. Just what I believe because when I pump I feel that pulling the penis it's just not using string or a stretching device but air or water pressure to cause the traction after it's expanded and grew last it's normal lengths, for girth past your normal girth of the penis and for the length traction starting after it hits past the normal erection size of your penis at this point it's pulling the penis (traction) even if it's not a stretcher device but water or air pressure expansion.