This is a L1430P locking male plug.

L1430P is a NEMA configuration code that sets standards for the electrical industry insuring interchangeability with other devices of the same designation.

The L1430P is a 4 prong male plug that is rated for 30 amps 120 or 240 volts.

These are  Marinco, or Eagle / Cooper brand, but will interchange with many other part numbers by manufacturers such as Leviton, Pass and Seymore, Bryant, Hubbel, Marinco, and many others.

These are made of Heavy Duty Nylon material and have a captive cord clamp for great connections to your cord. 

L1430P plug will plug into a L1430R receptacle or a L1430C female connector.

The L1430R receptacle is among the most common receptacles in portable generators, making this the most common plug to fit many portable generators made by Generac, Coleman, Honda, Yamaha Briggs and Statton.