This clips is a reproduction clips used by GM on many of the larger cars of the early to mid 60’s. Such as the Chevy Impala Buick and the Pontiac.
This clip is said to be used on the 1958 Chevy and most likely other GM cars of that era. It is new and the measurements are shown in the picture. When installed they press into a bathrub shapped hole in the body where the molding would be positioned. These clips are not being made today so what I have is what I have until I find some more at some later date.