White reproduction undercollar for M 35 or M 43 gymnasterka shirt.
18 1/2" (47cm) long by 1 1/2" (37mm)wide, tapered at both ends.
Brand new and "unissued."
Originally, "back in the day", undercollars were manufactured in dozens of specific sizes. These, however, are basically designed to be adjusted by the wearer to the length required.
While in garrison or on leave, soldiers would stitch a clean one of these into their tunic collars each morning.