The manual shows this as a 3057k. When I went to Napa warehouse they only had a 3057 and a 3057knal. I think those were all the letters... It was a yellow bulb so I didn't really care. What's the difference between the 3057 and 3057k? It fit and seems to work. I have to get a brake tag (inspection sticker) today so I had no choice. Anyone know why the 'k' specification in the manual?

TIA,
robert