Quote Originally Posted by taslucas View Post
What does the H4, H5, etc relate to?

Tap, crackle, pop
Those are the type (or style if you prefer) of the bulb mounting and filament design. H4 is a reasonably standard headlight style but later vehicles are moving to more exotic types... H3 is common in many spotties

Sorta like Bayonet versus Edison style light globes at home