Replacement Parts for British Berkefeld Filters Keep your British Berkefeld Gravity Water Filter System working great! We offer these replacements parts in case you need a spare: Black Plastic Tap - Comes standard with the Duchess, Duke and Prince. Stainless Steel Tap - A metal alternative to the plastic tap (fits Duchess, Duke and Prince); a great upgrade with improved flow rate and precise on/off control.. Washer - Comes standard with every filter element and is necessary for installation; compatible with the Ultra Sterasyl and Ultra Fluoride.. Wingnut - Comes standard with every filter element and is necessary for installation; compatible with the Ultra Sterasyl and Ultra Fluoride..