Pos-T-Vac Mach Ring Small #5 - REPLACES URMACH1TENSIONRING5.Mach Ring (SM) #5 inside diameter is 6.5 mm (.25 inches).PosTVac Mach Ring has a thick center, creating an evenly dispersed tension and comfort over a wide area.The Mach Ring will maintain adequate firmness for approximately 30-40 uses. Latex Free.