The Shure URT2 - Rack Tray For BLX4/BLX88/GLXD4/PG4/PG88 is a 1RU 19" rackmountable metal tray designed for supporting Shure's PG, SM, and Beta Analog Receivers BLX4 and BLX88. The tray has pre-drilled holes for fasteners to secure the PG4, PG88, PGX4, PG