The Scrotal Shield for PosTVac Penis Pumps prevents your testicles from being pulled into the pump cylinder when pumping and also helps protect the penis during use. This scrotum shield also aids in creating an airtight seal if your pubic hair is untrimmed or you do not have Timm Medical Sealing and Lubricating Gel to use with your pump. Choose the size that most closely matches the diameter of your erect penis. Once you achieve an erection and the tension ring is in place, remove the PosTVac Scrotal Shield to proceed with sexual activity.