NK was the brand of Nankai Tekko Co. Ltd. based in Osaka, Japan. From the 1950s to the 1970s NK were one of the leading Japanese manufacturers of coaster brake hubs. These hubs were branded either 'Nankai' or 'NK' or both, depending on something-or-other. More recently NK have positioned themselves as specialist manufacturers of 'freecoaster' hubs. These are components that are dearly loved by Freestyle BMX-ers, and so are, by definition, incomprehensible to the rest of us.

NK is listed on this site because in the second half of the 1950s NK launched a pull-chain derailleur. This marvellous object was supplied complete with a separate, sprung, chain tensioner for the TOP chain run. This allowed it to be used with a three speed sprocket cassette on a coaster brake hub.