Porcelain Ceiling Lampholders - Pull Chain features high-strength insulator porcelain. Mounts on 4" (101.6mm) outlet boxes with breakout for 3.25" (82.55mm) box mounting. Pull chain socket interiors are removable. Pull chain devices include ball chain, 3' (0.91m) of cord, connector, and end bell. Top wire versions have terminal screws backed out — ready for wiring — without removing the interior. Sockets are available in two-piece version to permit interior replacement, dust ring protects against plaster