Pos-T-Vac Mach Ring Medium #6 - REPLACES URMACH1TENSIONRING6.Mach Ring 6 inside (M) diameter 8.6mm (.340 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.