Connected flexible 2 x 2 white plates - what set?
That's an old 650 Hinge Coupling Nylon - Two Connected 2 x 2 Plates from the 60s.



It only ever came in 20 sets, but it's typically clear. It's listed as a possible alternate for the following set, but it's possible other sets could have had it as an alternate too.

901-2 2 Large Wheels with Accessories