On May 8, 4:55*pm, J Burns wrote:
SS is straight shaft and CS is curved shaft. *That probably determines
whether your arbor has RH or LH threads. *A replacement head would need
the matching thread direction, diameter, and pitch.

Thanks to all. My trimmer is a Straight Shaft.

Colbyt, how long does a pre-cut string typically last? I imagine I'd
need more than one per trimming, as I've typically needed more than
one "bump" per trimming.