This is one piece of high-temperature silicone rubber O rings for OD 25 or 50 mm quick flange sets. (Sold in a quantity of one piece) Materials: Silicone ID: 25.8 or 27.2 mm (see photo below) W: 5 mm (see photo below) Used for MTI EQ-FL-25KF25 or EQ-FL-50KF50 , please choose from the options bar. SOR25QF OD: 31.4 mm ID: 25.8 mm W: 3 mm SOR50QF OD: 57.5 mm ID: 47.2 mm W: 5 mm