This is the weatherstrip on the leading edge of the rear quarter window that seals between the back of the door glass and the front of the quarter glass when the windows are up. Sold in pairs.
1968-72 Cutlass and 442 holiday coupes and convertibles
1969-70 Oldsmobile 88 & 98 holiday coupes and convertibles
1969-70 Cadillac 2 door hardtop and convertibles except Eldorados
1968-72 Buick Skylark and GS two door hardtops and convertibles
1969-70 Buick LeSabre, Wildcat and Electra two door hardtops and convertibles