This compact chain tensioner may be small but it is top quality. Due to the ingenious use of a double-threaded screw, it adjusts from 1cm in reach all the way up to3cm. New design uses a 4mm wrench. Fits drop-outs up to 8mm thick or just over 1/4" - like those on most Aluminum and Steel BMX frames! Made in Japan by Mikashima ( MKS). One tensioner per package.