3 Terminal Round Junction Box 30 amp Surface mounted Powermaster 30 Amp 3 Terminal Junction Box Round | 1434-32 The Powermaster 3 Terminal Junction Box - 30 Amp has three terminals and is a standard white bakelite box. It is used to junction 6 square twin + earth cable. It is surface mounted. The pack contains one terminal junction box and has hassle free, easy to open polyurethane packaging. It requires standard installation tools and should only be installed by a competent, qualified person.