Insulators as follows -- actual postage additional:

U-629C no markings - cobalt blue -- no issues -- $8

U-281 no markings - nice green -- no issues -- $15 (SOLD)

U-601 no markings -- deep speckely cobalt -- no issues -- $8

U-295A no markings - green! -- no issues -- $15 (SOLD)

Take all four for $35