This linkage arm is made of heat treated cast alum. to offer the racer lightweight and fits Bug, and early Bird catcher injectors that use the 5/16" serrated shaft or the Bird, Buzzard and Big Ugly with a 7/16" serrated shaft.
With these link arms it makes it easy to hook up a throttle cable as well as a return spring.
Billet arm has 10/24" threads on one end and the other end has 1/4-28" threads for the throttle cable. RBS recommends #2200-0027A or #2200-0027B with the billet arms.