Podvorotnichok
A podvorotnichok (Russian: подворотничок, lit. 'undercollar'; [pədvərətʲnʲɪˈt͡ɕɵk]) is a type of sewn detachable collar used on the inside of collars of military uniforms that originated in Russia. It is a soft white fabric sewn into the inside of a collar to alleviate chafing and rashes, and to reduce wear and tear on the collar.