The flag of Kostroma Oblast, Russia, is a rectangle with width/length proportions 2:3 consisting of three vertical stripes: two red ones (at the edges, 1/4 of the flag length each) and one blue stripe (in the centre, 1/2 of the flag length). In the centre of the blue stripe there is the main element of the oblast cost of arms (its height is 1/2 of the flag width, and its width is 1/3 of the flag length).