[1] This is a round metal prefocus base 14.5 mm in diameter with a flat and two dimples so the H1 can be installed in a lamp only in the one correct orientation.

These same changes can be made with different parameters to give output identical to a standard bulb, but with lower power consumption.

These include high-wattage lamps, and those that emit light of a colour outside the white or selective yellow specification ranges.

Such lamps are illegal throughout the industrialised world for use in regulated automotive lighting devices, and so vehicle wiring, switches, and lighting components are generally not designed or built to withstand the higher heat and power consumption from off-spec lamps.

[3] There is considerable variability by jurisdiction in the regulation of off-road applications of lamp types used in on-road vehicles.