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 application temperatures between -45 degrees C and 165 degrees C by ASTM as 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 zipper 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: 20pcs 7/32" x 1/16" 20pcs 1/4" x 1/16" 20pcs 6.8 x 1.9 20pcs 5/16" x 1/16" 20pcs 7.8 x 1.9 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 pieces 14x 2 10 pieces 15x 2 10 pieces 17x 2 10 pieces 11/16 "x 1/16" 10 pieces 11/16 "x 1/8 " Size: 20.5cm*10.5cm*3cm Package Weight: 154g green color Package List: 270 x Auto Air Conditioning O Rings Set