Screwless Telephone Master Socket -Anthracite IP20 | Description: The master socket contain a surge arrestor and an R/C circuit filter these are used by your service provider to get a fixed value resistance when they run line checks. Standard BT type socket with screw type terminals. Flawless Screwless design - Master BT type socket - Screw terminals - Screwless low profile design with built in gasket - Certified to BS 5733 - Minimum mounting box depth: 25mm | Features: Finish: Anthracite, Material: Premium grade steel, Height: 8.75cm, Width: 8.75cm, Projection: 0.43cm, Wattage (max) : 2.5W