JBL MTC-48TRX4 Ceiling Speaker Tile Rails for 4' x 4' Ceiling Tiles (Pack of 4)This accessory tile rail set is designed for configuring JBL ceiling speaker installations in suspended ceiling grids with spacing up to 48" (1200mm). It supports 4 ft x 4 ft ceiling tile applications and works with JBL models that use the C ring tile rail mounting system. The inverted V groove helps support the tile rail grid in case of tile failure while reducing vibration transfer and rattling through the ceiling tile grid system. The 0. 05" (1.