Lower track for the sliding glass door consists of a slippery vinyl extrusion which provides anti-rattle sliding action for glass doors 3/16" to 1/4" thick. The extrusion is 12 feet long, easily cut-to-size. The lower track inserts into a groove 3/4" wide x 1/2" deep. The lower track is used with the P102603B upper track. Dark brown, walnut color.