Glass, reflector and light bulb inseparably combined in one unit: the sealed beam headlights invented in 1939 were mandatory in the US from 1940-1983, at least for cars, and were standard on Harleys from 1948. Older designs such as the Springer headlight on the Harley have separate parts instead, and in some cases the bulb even had to be positioned with an adjusting screw. Also, the reflector had to be checked regularly for rust, as there was often moisture inside due to inadequate seals. The sealed beam insert put an end to all this.