Individual types are A, B and C ( left to right in illustration). Screw Termination Shrouded Plugs. High quality plugs for cable up to 2.5mm 2. Maximum insulation diameter 3.9mm. Available with either fixed or retractable shrouds. The fixed-shroud version is also available in stackable type. The retractable shroud in-line plug has a protective collar to define the safe handling area and prevent accidentally touching the contacts. Contacts are nickel plated brass with Beryllium-Copper lantern springs