Bikemonger says.... This is the tensioner that started it all off, updated, it is still a great bit of kit.
Surly says..... Spring loaded chain tensioner for running singlespeed on non-adjustable chain tension frames.
Fits to rear mech hanger position.
Surly Singulator features CNC alloy body, variable chainline, floating tension pulley, stainless steel pivot bushing, triple sealed reversible spring.
Compatible with 1/8" and 3/32" chains.
11t jockey and slotted alloy chain rejection side plates.
All in all... the mutts nutts of SS chain tensioners.
Arm length 70mm
Lateral adjustment 40mm
Maximum recommended cog size 24t