"mm" wrote in message
...

What size string for a string trimmer?
. . .
Is there a problem using string too thin? Or too thick? How do I
know what to use?

You should use the thickest that will auto-feed on demand.
Thinner string both erodes faster in use and is more prone
to jam on the supply reel.

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)