The BG12TR is intended for indoor use and is designed to be snapped onto the back of a BG12 Series Manual Fire Alarm Pull Station (prior to wiring device). The trim ring provides an additional 1/2” (12.7mm) of clearance on all sides as well as accommodating electrical boxes protruding from the wall surface up to 1/8” (3.175mm). This trim ring allows installers to retrofit applications where a larger pull station was previously installed.