These fittings are NPT (National Pipe Thread) and available in 1/8, and 1/4 inch. Simply select the proper thread type that matches your cylinder, solenoid, or other threads you are using. Click here for information on selecting the proper thread sizes for your application. And also select the proper airline size for your application.
These are self-sealing, no pipe dope or Teflon tape required.
These fittings accept 1/4 inch (inside dimension) airline (tubing). The airline simply pushes into the push-on fittings and allows the hose to swivel. You can find the proper airline here.