If you are wanting to use the L7 bolt on the Rev-I or Threshold this is the back cap you will need to use with it. Made from aluminum and made right here in the USA. This part is great because now you can take your bolt out with the use of no allen keys. This back cap is different than the one that comes with the G4 Bolt Engine and the G3 Bolt Engine. If you have a REV-I or Threshold this is the back cap you need. This cap is meant to replace the back cap with the pressure gauge because the L7 bolt has no forward access. The gauged back cap will not work with this engine.