Encore Individual Tension Rings, Size 3 1 2 inch, 8 Pack Hydrogels These are removable zippered polyester These are removable zippered polyester cover is low shear Also feature Leak Block sides and neutralize odor on contact One of the important qualities of vacuum therapy products is that they can aid in restoring sexual function without the use of drugs and are less costly and less invasive than surgery The Individual Tension Rings made by Encore Medical are replacement rings that are used with the Food and Drug Administration or FDA approved vacuum therapy products designed for the medical conditions known as Erectile Dysfunction or impotence