Plug Style GHT1.  3/4" female garden hose threads with seal.   Used in conjunction with The 'Cooler bleeder, Series 2 Adapter, and Universal Tee / T-fittings to adapt to custom fitments or vehicles that have had the factory bleed port eliminated.
 
Also used on Magnuson TVS2300 C7 LT4 Corvette bleeding, where Magnuson has provided a Tee port to fill the system
 
See Connection Chart for fitments or used in universal and custom applications.  
 
Note:  Hand assembled in the USA, there may be cosmetic tooling marks on plug from assembly.