I dont know, but truthfully I dont even think its possible..
And I've done some experimenting
First of all, Even with a
cock ring, you cant stay 100% erect for an hour straight.
And secondly, for me, jelqing at 80% is no different than jelqing at 100% my dick expans all the same, and it saves me the cost of pain, I always start jelqing at 100% but I end up being back down at 80% and theres no difference..
The same goes for the squeeze, if I squeeze at 80% than I still get the same expansion as I would with 100%.. [words=https://officialhydromaxpump.com/?uid=6&oid=2&affid=98 ]
Hydromax[/words].