I have the oro-stimulator.
It is basically a sleeve made from that silicone cyberskin that attatches to a dome that is then connected to a hose that connects to a pump of sorts to create a vaccumn. Its almost like a penis pump without except the cylinder is soft. It simulates a blow job.
When you pump, the whole thing goes up and down your shaft, like a mouth going up and down your shaft. It feels close to the real thing. I could cum by just pumping. A hands free cum. The vaccum is just enough. And the whole thing is under $20 bucks.
My sleeve ripped at one point so I bought a new one. The new one had bumps on it for extra stimulation. I dont use this that often because I do not want to get too used to it and cheapen the effect. Sometimes I will jerk off using just the sleeve.
Length is not an issue but I imagine girth would be. One one version, Julian Rios is demo-ing the product on the cover picture. If you are over 5.75 inches in girth, I dont think you could fit inside the sleeve or the dome thing.