Activities Sports & Athletics Paintball Tank O-Ring Replacement What size to get and how to put it on Share PINTEREST Email Print Miguel Villagran/Getty Images News/Getty Images Sports & Athletics Paintball Baseball Basketball Bicycling Billiards Bodybuilding Bowling Boxing Car Racing Cheerleading Cricket Extreme Sports Football Golf Gymnastics Ice Hockey Martial Arts Professional Wrestling Skateboarding Skating Soccer Swimming & Diving Table Tennis Tennis Track & Field Volleyball Other Activities Learn More By David Muhlestein David Muhlestein is a paintball and woodsball enthusiast who has been playing since the mid-1990s and has extensive knowledge of paintball equipment. our editorial process David Muhlestein Updated May 14, 2017 O-rings are used in paintball guns to seal off spaces, ensuring that air does not leak from the gun. You typically find an o-ring wherever two pieces of metal connect and air passes through. O-rings are a vital part of the paintball gun but periodically need to be replaced. Replacement When you clean your gun, check your o-rings for any cracks or warping. If there's a problem, remove the o-ring by either cutting it and pulling it away or using a sharp object (like the end of a nail) to pull it away from the gun or tank and then slide it off - be careful not to scratch the metal. After sliding a replacement o-ring on, put a drop of gun oil or grease on the o-ring and smear it completely around. Sizes Depending on the gun, many different sizes of o-rings are used. Fortunately there is a standard o-ring that almost all paintball guns use and it's the size you typically need to replace. It is commonly available from paintball stores, large retailers (such as Wal-Mart) and is readily found online (Compare Prices). This standard size o-ring is used for tanks (both CO2 and compressed air) and is typically found on bolts and strikers. If you buy the o-ring from a non-paintball retailer, look for the standard 015 size o-ring - it has an inside diameter of 9/16th of an inch, an outside diameter of 11/16th of an inch and is 1/16th of an inch in diameter. For other sizes check contact your gun's manufacturer to find out what sizes of of o-rings you need or buy a rebuild kit that has all the required sizes included. Materials Replacement o-rings are typically made of one of two materials: buna or urethane. Buna or Buna-N is a compound of butadiene and acrylonitrile and is black. Urethane or polyurethane is a clear or whitish color which can yellow with time. Most guns and tanks come with urethane o-rings, which last slightly longer than the buna o-rings, but they also cost more. Either one is a fine replacement.