Considered by many to be the smallest, most attractive proximity reader available, the MicroStar is designed to mount directly on a metal window/door frame (mullion) or any other location a small reader is required. Size is just 3.4" x 1.4" x 0.38" (86 mm x 36 mm x 10 mm) with a read range of up to 4" (10 cm). Lifetime warranty.