Pentek OR-34 O-Ring for Culligan Whole House Water Filtration System – The OR-34 O-Ring has been branded under Ace Hardware, American Plumber, Ametek, Culligan, Pentek, US Filter Plymouth Products. The OR-34 rubber o-ring gasket is 4.125″ in diameter and is a Buna-N o-ring. The Pentek OR-34 o-ring gasket should be lubricated with silicone lubricant to prevent leaks in the water filtration system.