The Barnett J4B is a small gyroplane marketed in the United States by Barnett Rotorcraft for homebuilding. Originally flown as the J-3M with an open cockpit and fabric-covered sides, later versions have a fiberglass cockpit pod either partially or fully enclosing the pilot. Apart from the basic J4B, versions available in 2007 included the BRC540 (two seats side-by-side) and J4B2 (two seats in tandem).