Culligan OR-100 O-Ring for Big Blue Housings 1" Housing O Ring For Heavy Duty Sediment Water Filter Use With Model #HD-950A 1" Housing O Ring, For Heavy Duty Sediment Water Filter 1" Housing O Ring, For Heavy Duty Sediment Water Filter, Use With Model #HD-950A The OR-100 O-Ring has been branded under Ace Hardware, American Plumber, Ametek, Culligan, Pentek, US Filter Plymouth Products. The OR-100 o-ring is a lubricated rubber gasket for Big Blue whole house housings. The OR-100 is NOT for Big Clear housings. The OR-100 rubber o-ring gasket is 5.75" in diameter and is a Buna-N FDA grade o-ring. The OR-100 o-ring gasket is used to seal the housing sump to the housing cap to prevent leaks. The Pentek OR-100 o-ring gasket should be well lubricated with silicone lubricant to prevent leaks in the water filtration system.