This specially made sleeve fits into the Autoblow Ultra stroker case that comes with the Autoblow Ultra machine. The stroker case is also available separately.. With the addition of the Vacuum Cap, this sleeve turns your Ultra’s stroker into a super powered vacuum stroker by sucking all of the air out of the stroker case and then dynamically pumping the air back in over and over again, leading to a completely new and absolutely amazing pleasurable sensation for your penis. This special sleeve comes in two varieties: regular fit and extra tight. Be aware that you do need an erection to penetrate the extra tight sleeve as the hole is small and tight to ensure a perfect vacuum while inside.