They're 1:43 scale. Why in the world did they pick 1:43? They aren't the same scale as anything that I've ever built. I've built planes in 1:32, 1:35, 1:48, 1:72, but never even SEEN anything in 1:43.
Dumb.
Brumm has been making die-cast automobiles in that scale for several decades...it's a standard scale for die-cast car collectors (along with 1/25th), just as 1/72nd or 1/48th are for aircraft model-builders, and 1/35th is for armor builders.