This FFKM - FFPM O-Ring is 491 x 7mm and in the color Black. The Hardness of this O-ring 491x7 - FFKM - FFPM - Kalrez 6375 - 75 Shore A - Black - ORS177663 (Equivilent) is 75 Shore A.The alternative names of the compound are FFPM – Dupont Kalrez and they are mostly produced by Kalrez® - Simriz® - Chemraz® - Spectrum® - Triazinico® - Isolast® - Parofluor® - Fluorez® - Perlast® - Perfluor®. The O-ring is commonly used in and has an operating temperature range from -25 ºC to 270 ºC. O-rings 538657 are indicated as 177663 and have a DIN 3771 Size of 491 x 7. This item is equal to Dupont Kalrez 6375, Freudenberg Simriz 495, Greene Tweed Chemraz 605, Parker Parafluor V8910-75, PPE Perlast G80A, Trellebrog Isolast 9440 and has an None Approval. The chemical name of this Oring is Perfluoroelastomer.