Check the listing for details. 4 Pk Whole House Water Filter O-Ring Omni U30 Pentek Omnifilter (from Menards). Color: Black, Condition: New. Listed at 12.25 USD. This is for the whole house filter sold at Menards and elsewhere. They sell the O-rings there as well, but you have to buy a 4 pack and only one of them works for the U30. Here you get a 4 pack all for the U30. These also fit the Pro Water Parts filter housings 2.5x10"Whole house filter O-rings are essential components used in water filtration systems to create a watertight seal and prevent leaks. These O-rings are typically made from durable materials like rubber ensuring longevity and resistance to water and chemical exposure. They are designed to fit securely into the filter housing, providing a tight seal between the filter sump and cap. Properly functioning O-rings are crucial for maintaining the efficiency of the whole house filtration system, as any gaps or leaks could lead to water bypassing the filter and compromising water quality. Regular inspection and replacement of O-rings is recommended to avoid potential issues and ensure the system operates optimally. By providing a reliable seal, whole house filter O-rings contribute to effective water filtration, safeguarding the entire household's water supply from contaminants and sediments for improved water quality and safety.