The cup of the Ergo One Heel Grounder is a symmetrical design that can be reversed when put on. It also features three layer rubber, with a non-marking interior/exterior and a conductive rubber inner layer. As with all of our static control heel grounders the Ergo One Series has a 1.5” wide rubber, securing both at the back and underneath the heel. Its 7.5” length rubber provides enough cup volume to fit comfortably on those with larger shoe sizes.