This heel grounder's three-layer rubber sole has a black conductive inner layer sandwiched between two yellow dissipative layers that will not mar shoes or floors with black marks. Not having exposed carbon makes it ideal for cleanrooms. The bright yellow color can easily be seen from a distance, ensuring ESD program compliance. This heel grounder is also reversible, extending its useful life. Its adjustable hook and loop VelcroŽ fastening assembly provides comfort, and a conductive, nylon polyester, grounding strap guarantees body-to-ground contact on both sides of the foot.