FSA is a brand name of Tien Hsin Industries, which explains why the The FSA SureLock headset locknut originally started life as the Tien Hsin Double Lock – click to see more details.
Under the Tien Hsin brand name the locknut was only available in 1″ flavour, but this increased to 1″, 1 1/8″ and 1 1/4″ under FSA. The colour choices also increased to cover more popular colours.
Interestingly, the FSA branded Double Lock was later sold as an Acor Frankie headset locknut.
Colour: Black, Blue, Purple, Silver
Weight: 27g (1″)