Used seat track trim.  This is a single piece of trim, that attaches to the front of the seat track between the track and seat.  GM# 20356005. This is for the driver's (LH) seat track.  This has a crack in the top (See photo #3)  Fits the following:

82-92 Camaro (all models w/ 2-way manual track)
82-92 Firebird/Trans Am (all models w/ 2-way manual track)

The item in the photo is the actual item being sold.