Use to join a coax cable inside a wall to a coax patch cable outside the wall. Mounts to a wallplate with a BNC cutout. The WZ10102 and WZ10104 are just two of the many wall plates this can be used on, just look for the "01" as the third and fourth characters of a wallplate part number (Wxx01xx). Signal loss may be equivalent to about 10 feet of cable (so joining two 30 foot cables with this will be 60 feet but will have the same loss as a 70 foot one piece cable). Most coax applications have length limits around 300 feet. This works on Thinnet™, Arcnet, Audio & Video (where BNCs are used).