Features: Hydrogenated Nitrile Butadiene Rubber (HNBR), also known as Highly Saturated Nitrile (HSN) is a special class of Nitrile Rubber (NBR), HNBR can be formulated to meet at application temperatures between -45 degrees C and 165 degrees C per ASTM as a Type DH polymer. Heavy duty rubber rings are available for applications requiring higher chemical resistance and higher temperatures than NBR. The O-ring assortment set is packaged in a clear plastic zippered case with identification compartments. 270pcs in one case totally and 18 kinds of o-rings per sizes. Suitable for professional ironing, supplies, tools, automotive, garage, plumber, mechanic, workshops, repairs, air and gas connections. Specification: 20 pieces 7/32"x 1/16" 20 pieces 1/4 "x 1/16" 20 pieces 6.8 x 1.9 20 pieces 5/16 "x 1/16" 20 pieces 7.8 x 1.9 20 pieces 8 x 2 20 pieces 8.8 x 1.9 15 pieces 7/16 "x 1/16" ; 15 pieces 7/16 "x 3/32" 15 pieces 11 x 2 15 pieces 12 x 2 15 pieces 13.9 x 1.8 10 pieces 9/16 "x 3/32" 10