Captain O-Ring - Benjamin & Air Force PCP Hand Pump ORing Rebuild Kit (Polyurethane Piston O-Ring Upgrade) Product includes a link to our printable o-ring replacement guide, making replacing your o-rings easier than ever Includes all o-rings needed to rebuild your Benjamin/Air Force PCP Hand Pump Includes polyurethane piston o-ring, which is better suited to handle the abrasion that destroys buna o-rings when used on the piston rod Printable o-ring replacement guide is available at captainoring.com/manuals Manufactured and warrantied by Captain O-Ring LLC