These Tension rings are medically engineered for safety, performance and comfort. The unique upper extruding bumps are positioned to press against the veins that maintain an erection. The lower urethral notch allows for ejaculation. The rings may be used individually or in various combinations to maintain an erection created by the Vacuum Pump. The User Guide details seven possible combinations to accommodate a wide range of penile girths. Rings are latex-free and should be replaced every six months, pending usage.