Track-Lites White Track Head. Drawn steel housing with polycarbonate stem. Medium base porcelain socket with nickel plated copper screw shell. Copper alloy contacts provide precise spring action. True, positive electrical ground. On/off switch included. Patented embossed polarity arrows on bottom of adapter. Spring loaded locking latch with embossed polarity arrows secures trac light to trac. Compatible with both Trac-Lites and Trac-Master Trac. Pull-up contact to up position for use on Trac-Master two circuit trac. UL/CUL listed.