This item is used on multiple models.
REPLACES ORIGINAL NUMBER 5-320 ON SOME REELS
HOW TO IDENTIFY THE NEWER OR OLDER GEAR PAIRS:
Penn changed the design of the main and pinion gears at some point. The easiest way to tell which pair that you have is to look at the main gear, holding it sideways to look at the teeth.
On the newer style 5N-320 main gear, the teeth are all one straight edge. On the original 5-320 main gear, the end of the teeth has a edge tapered at an angle. Photo sample below using a 5-310 gear since it has the same style edge as the original 5-320 gear.
If you are replacing an older style 5-320 gear with the 5N-320, you will also need to replace the pinion gear with the matching newer style 13N-320.