his solenoid plug screws in place of the existing electronic boost solenoid found on the He351CW turbo. All plugs are CNC machined from 6061 aluminum. By installing only 2 of the 3 included O-Rings, you can use the actual nipple on the cold side for boost reference/control. By installing all 3 O-Rings, the whole thing is sealed. O-rings are not provided with the plug you can use the ones off your solenoid or purchase new ones at your local parts store.