Lampholders mount on 4" (101.6mm) outlet boxes with breakout for 3.25" (82.5mm) box mounting. Leads are 6" (152.4mm) 221ºF (105ºC) insulated stranded #16, stripped 0.75" (19.0mm). Pull chain devices include ball chain, 3' (0.9m) of cord, connector and end bell. Top wire versions have terminal screws backed out â€“ ready for wiring without removing interior. Porcelain models made with high-strength insulator porcelain; pull chain versions feature removable interiors.