The cup of the Day Glow Heel Grounder is a symmetrical design that can be reversed when put on. It also features a dual layer rubber with a non-marking inside and a conductive rubber outside. 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. It’s 7.5″ length rubber provides enough cup volume to fit comfortably on those with larger shoe sizes.