Fixed Gimble Fitting Lampshade Wired from the top, these fittings sit on top of the lamp base socket. A threaded ring (supplied with your lamp base) screws on top of the washer to keep the fixed gimble fitting in place. Washers can be 42mm (ES), 28mm (BC or SES) or 20mm (SBC). Please stipulate how high you would like the washer to be set.