Material: Our 3.5" o.d water filter o-ring is Made of high quality nitrile rubber that is flexible, wear-resistant and tear-resistant, not easy to aging and oxidation, longer service life Compatibility: Compatible with FOR APEC Essence and Ultimate reverse osmosis systems and can also be used in most industry standard size 10'' filter housings Easy to install: The replacement O-rings are flexible, easy to install and remove, durable and unbreakable. Simply remove the broken O-ring, apply silicone grease to the O-ring that needs to be replaced, and place it back in the groove Seal leak: The water filter housing o-rings can be combined with any food-grade lubricant to provide a good seal and allow the filter to maintain optimum filtration efficiency Function: Reduces friction in equipment and prevents leakage of liquids or gases