The device is designed so that the snapping sound caused by {HEAD ~ the plunger} hitting {TAIL ~ a wall} synchronizes with the impact on the muscles felt by the user during a hand motion 
hitting
The device is designed so that the snapping sound caused by { HEAD ~ the plunger } hitting { TAIL ~ a wall } synchronizes with the impact on the muscles felt by the user during a hand motion
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH