I was told by Home Depot that the Electric Hybrid Trimmer Head would not fit on the CMCST910M1 trimmer. Well I ordered one and guess what? Fits perfectly with no problems and works just fine...hmmmmmmmmmmmmmmmm!
Took the blade off and it balanced perfectly, however, the nut that goes on started to turn round and round. Have to get a new nut, but used thread lock on it and it is holding ok..no more shut down noise.