The big question when it comes to the ol' in and out is who feels what and where. And no matter how good the getting' is, it can only feel better with an extra sensation or two. That's the idea behind Senso Enhancers. They come three to a package, and are very stretchy jelly rings which slip onto one's dangle when it's time to toss the timber.
During our unofficial, almost scientific trial (we employed UC coeds with science majors), one ring ripped, but the other two functioned as promised, although responses varied from enthusiastic "Oh fuck yeah," from one blond biochem student, to a rather blah "Well, it kinda tickled -- does that count?" from a petite Asian statistician.