This is a set of wardrobe items created for use in the Star Trek feature films for wear by Starfleet crewmen - these show up quite noticeably in Star Trek VI: The Undiscovered Country. The item is a red trimmed engineering division strip. The item is yellow fabric bordered by red trim intended to be affixed to a Starfleet crewman's costume left forearm sleeve and comes with a pair of yellow hued division strips for placement on the shoulders of the said costume. The item features holes where additional elements were removed previously and the ends are sewn together allowing for a sleeve with a three inch diameter opening to fit within. These were used with the maroon-dyed jupsuits that were first introduced as white in the first movie.
A screen-cap is included for reference.
More from Star Trek VI: The Undiscovered Country (1991)