The PPD BSPT Male Straight is typically used with bags from Taiwanese manufacturers like AirREX and D2 Racing since BSPT threaded ports tend to be a standard on their products. The standard PTC end of this fitting makes connecting and removing your air line from these bags extremely simple. No more messing around with those compression elbows!
Certain installs might benefit from the PPD BSPT Swivel Elbow instead.