I actually gained a few milliters in girth with an extender; but ony just under the glans and (big point IMHO) with a noose -style extender. I think this is due to the noose partially blocking the blood flow. Ain’t the same growth you are going to have with jelqs - I mean most of people aren’t going to gain girth in the whole shaft or most of it.
Just have underhand the full Gontero’ study, which is generally considered the best on the topic:
"….
Among conservative methods, it has been claimed that penile extenders can increase penile circumference by 0.6–1 cm/month [22]. It is not clear why these devices should be effective in enhancing penile girth; it has been hypothesized that chronic traction causes soft tissue cellular proliferation with tissue growth in a multiplanar fashion [19]. These findings, however, were not confirmed by a study by Gontero et al. [7], who found only negligible changes in penile girth after 6 months of traction therapy.
Nikoobakht et al. [16] did not find significant changes in proximal penile circumference, either, although a significant difference was found in glans penile circumference. It is interesting, however, that no girth decrease was reported with traction therapy, as one would have instinctively thought."
http://onlineli brary.wiley.com … 10.09647.x/full
(Yep it is, since we also have a few threads started by people who claim stretchers made their penises skinner ;) ).