[1][2] The MH-1 was originally provided as a series of kits to upgrade old Mini-500 airframes, allowing the owner to modify them to MH-1 standards.
The remaining kits cover modifications to the main transmission, the tail, main drive and clutch basket, radiator fans and relay and the rotor head.
In either case the resulting MH-1 complies with the US experimental - amateur-built rules.
Its 19 ft (5.8 m) diameter two-bladed rotor has a chord of 8 in (20.3 cm).
[1] The Federal Aviation Administration approved the MH-1 conversion as a distinct aircraft type.