Express end cap For John Deere OEM Stainless Booms or 17mm Nozzle body Port SizeFits John Deere 17mm Port Size. If you have factory installed John Deere High Flow or Stainless Steel Plumbing. You have a 17mm port size for the jumbo nozzle bodies. These 17mm express ends are the ones you need. Conventional boom designs trap air in the boom causing a delay from the close signal to when spray actually stops. Pentair's Hypro Express nozzle body end caps include a passive feature that eliminates the trapped air by allowing the air to