The 867 series has been designed for surface mounting with the gray, corrosion resistant, surface mount box supplied with the unit. The box measures 5-5/8 in. (143mm) square by 3-5/16 in. (84mm) deep. The 867 series electronic horns are designed for use in corridors and manufacturing sites. It is used wherever a distinctive, audible signal is required for timing, scheduling, general alarm, and warning applications.