Set of (3) ECHO Echomatic Pro Trimmer Heads Part Number #21560031 This model fits ALL ECHO Straight shaft trimmers This item comes with 3 of the heads!!! (If you purchase this head and cannot get it installed here is a link to a video explaining how) How to Replace Your ECHO Head This head is a Echomatic pro trimmer head. This head comes pre-loaded with 0.95" diameter ECHO line. it can fit up to .155" line. These heads fit ALL ECHO straight shaft trimmers, (this includes, but is not limited to) SRM-210, SRM-210I, SRM-210SB, SRM-210U, SRM-225, SRM-225I, SRM-225SB, SRM-225U, SRM-230, SRM-230U, SRM-260, SRM-260S, SRM-261, SRM-261S, SRM-265, SRM-266, SRM-311S, SRM-340, SRM-400U