This item is used on multiple models.
Fathom Star Drag Models Part Issue
The Fathom series of reels (Models FTHSD12, FTHSD15, FTHSD25N, FTHSD30, FTHSD40)
Early schematics for these said to use the 120-113H O-Ring under the spool tension cap, but this is thicker than what is on the reel and the cap will not screw down over this fatter O-Ring.
FOUND WORKABLE RING:
Use the 120-SQLLW
on the Fathom tension cap instead.