Bosch H4's were introduced in late 1972. The H4 bulb had two filaments which enabled the headlight to contain only one bulb and thus one reflector, unlike the H1's. H4's became an immediate favorite and were used by the Porsche for all of their rest of world (RoW) cars until the 993 that was introduced in 1993.
Restoration includes the following steps:
- Reflectors – stripped, copper plated, nickel plated, polished, followed by vapor deposited aluminum plating, silica layer – Why aluminum?
- Housings – media blasted and powder coated
- Lenses – new with correct Bosch lettering
- Lenses Gaskets – new
- Chrome Trim Rings – new
- Adjustment Screws – mounted with nylon lock nuts for easy removal
- Fender Mounting Screws
- Fender Mounting Gaskets – new
- Bulbs – new, 60w/55w or 100w/55w (relay kit recommended for 100w)
- Bench Tested