by justDIY » Mon Oct 12, 2015 12:26 am
never used one myself but have studied the device somewhat.
from what I've seen online, the cheap ones have a rubber sleeve for you to insert into, and then motorized rollers that go back and forth (up and down maybe?)
The super expensive ones are dual-suction based, a sleeve fits over a cylinder and you insert yourself into the sleeve. the sleeve provides more or less constant suction of adjustable strength to "hold on" to your member. then the space between the cylinder and sleeve is either pressurized or suctioned, alternating in speed and volume, creating a pulsating effect.
The inbetween priced ones use a single suction source that alternates between suction and pressure, so the sleeve slides up and down your member.