This item is used on multiple models.
On 955, 965, 975, 975LD, 975CS 975CSLD:
Left Side Plate Short Screw
On TRQ15LD2G, TRQ25NLD2G, TRQ30LD2G, TRQ40NLD2G:
Cover Screw (uses 4)
On TRQ100LD and TRQ300LD:
Drag Cover Screw (uses 4)
On 525GS, 525MAG, 525MAGT:
Right Side Plate Screw
For the 525MAG REELS ONLY: The older reels used the fine threaded 39S-965.
Later models use the coarse threaded 39-525
To figure out which one your reel uses, here is a comparison photo: