The almry204 spool head assembly kit is compatible with a range of dual line models the kit contains 1x housing 1x spool line 1x spool retainer bump knob1x spring it is supplied with 516unc x 12 inch right hand thread bolt the almry204 fits challenge extreme ryobi sears craftsman toro trimmer models including pg 07 34cc 100r 125r 130r 135r 305 rt 306 rt 700r 710r 720r 740r 750r 760r 764r 765r 766r 768r 770r 840r 920r 960r 970r weedwacker 71 51315 71 51316 71 51715 71 51425 curved shaft 16 inch