Compatible with Garelick hardware. Provides solid base of support for a variety of seat hardware. Accepts Garelick fore and aft seat slides and 360° swivel spider combinations. Accepts seat slides 21000, 75080, 75081, 75082, 75083. Accepts spiders 99023, 99026. 2-7/8" diameter ribbed stanchion tube, 9.25" diameter 6 hole base plate.