The COM is a heavy duty-version of the AC-43.
Should have a larger center electrode and wider ground tab, making it last longer but otherwise the same.
It was used in 2 to 2-1/2 ton trucks with 261 and V8 engines for city operation.
Also recommended for the smaller truck 235 in continous heavy duty operation.
My drivers never need colder plugs than AC-44, even when driving on the freeways for hours during the hottest summer months, around 2500-3000 rpm.
