The MS-5000BX is a smallest readers, the MicroStar Reader measures just 3.4" long x 1.4" wide x 0.38" thick (86mm x 36mm x 10mm) thick, and is designed to mount on a metal window or door frame (mullion) or directly on a wall. Read range is up to 4" (10cm). The MiniStar Reader measures 4.3" long x 3.0" wide x 0.38" thick (109mm x 76mm x 10mm), and can be mounted on a single gang electrical box or flat on a wall. Read range is up to 6" (15cm) when mounted at least one inch off metal. If the reader is mounted using a metal electrical junction box with the thickness of the wall material separating the reader from the box, read range will be reduced.