Spectrum Drilling Tools International manufactures Kelly bushings – both Pin Drive & Square Drive, which conform to the latest edition of API-7K specifications and are duly API-7K monogrammed. We also offer NOV Equivalent Kelly Bushings. Our Kelly Bushings are designed for use with 17.5”, 20.5”, 27½”, and 37½” Pin Drive & Square Drive Master Bushings, capable of handling 3” to 6” Hex and Square Kelly.