Hi, The spare pieces are left after cutting out the Leader locker liners, which I sell at AOMCC rallies, auto jumbles etc. the spare bits being used to make both the Leader and Arrow coil covers. The material- mill board is 1.1 m/m thick, slightly less than the original which was 1.2 m/m thick.
Some classic cars have mill board door cards or similar but it was a bit thicker and embossed on one side.
You can have a piece of board enough to make an Arrow cover for free or I sell the covers+ two clips for £ 3-00.
Regards Brian H.