Used to prevent the mains'l slides from falling out of the sail track when the main is doused at the end of the day. When it's time to hoist the main again, just haul on the halyard and up it goes. No need to feed the slides into the track again. Fits your Catalina 22, Catalina 22 Sport, Capri 18, Capri 22, Catalina 25 and any model which uses standard 1/2" diameter round internal track extruded into the mast.
Includes large knurled nut. Slug in mast is 1/2" diameter X 7/8" high.
Vintage Catalina masts were machined by hand and if the sail entry slot is narrower than the 1/2" required for this stop, you can slide the stop up from the bottom of the mast or sand the sides of the stop until it will fit through the sail entrance slot.
Another option is to go with the original style stops, D1150, which require a screw driver to secure but are smaller at 7/16" in diameter.