... ringMaterial100% NBR(nitrile -butadiene rubber)Physical Properties1. Black NBR o-ring is excellent in electrical insulation, anti-aging/ozone/weather resistance ... ,2. Obturator o-ring.So it is light,resilient and stretch3. Workable under wide ... to its softness,it can apply for any irregularitties.What's more,it works well in preventing air/water/heat ...