Awakingdemi 270-Piece Air Conditioning O-Ring Assortment Rubber 18 Sizes for Car Auto Vehicle Repair Hydraulic Pumps Material: Rubber Assortment O-Rings with convenient resealable plastic case. O-ring has total 18 most popular used O-ring Sizes. Hydrogenated Nitrile Butadiene Rubber (HNBR), also known as Highly Saturated Nitrile (HSN) is special class of nitrile rubber (NBR) and is for mission critical applications. O ring rubber can be formulated to meet application temperatures ranging between -45 degrees C and 165 degrees C, and HNBR is classified by ASTM as DH-type polymer. Material: Rubber