Description: Hydrogenated Nitrile Butadiene Rubber (HNBR), also known as Highly Saturated Nitrile (HSN) is special class of nitrile rubber (NBR),HNBR can be formulated to meet application temperatures ranging between -45 degrees C and 165 degrees C, and HNBR is classified by as DH-type polymer. The heavy duty rubber rings is available for using in applications requiring higher resistance to chemicals and higher temperatures than NBR. The o-ring assortment set is packed by a snap-close clear view plastic case with compartments for identification. 270pcs in a case totally and 18 kind of O-rings by sizes. Suitable for professional plumping, supplies, tools, automotive, garage, plumber, mechanic, workshops, repairs, air &gas connections. Specification: 20 pieces 7/32" x 1/16" 20 pieces 1/4" x 1/16" 20 pieces 9/32" x 5/64" 20 pieces 5/16" x 1/16" 20 pieces 5/16" x 5/64" 20 pieces 5/16" x 5/64" 20 pieces 11/32"x 5/64" 15 pieces 7/16" x 5/64" 15 pieces 7/16" x 3/32" 15 pieces 1/2" x 5/64" 15 pieces 7/16" x 1/16" 10 pieces 3/8"x 5/64" 10 pieces 11/16" x 1/ 16" 10 pieces 11/16" x 1/8" 10 pieces 11/16" x 5/ 64" 10 pieces 9/16" x 1/16" 10 pieces 9/16" x 3/32" 10 pieces 5/8" x 5/64" Package Includes: 270 Pieces O-Ring Gasket Seals Kits Note: Please allow 0.5-1 inch difference due to manual measurement.(1 inch=2.54cm) Due to the difference between different monitors, the picture may not reflect the actual color of the item. Please understand, Thank you. Please check the size measurement and the picture carefully before making payment.