Slow retract manual operation screen

Manual operation screen: Product description : ---Roll up/down screen for school and seminar use. ---The standard design of the screen is for wall or ceiling mountin with slow retract system ,low noise . Screen Surface : --- Screen surface base on fabric base ; ---Black border: L, R, T, B, stand for Left, Right, Top, Bottom ---1:1 Size up to 240cm; Only 3cm for L & R. --- Size bigger than 240cm;Only 5cm for L & R. --- 4:3 Size up to 240cm; 3cm for L & R & B, 5cm for T. --- Size bigger than 240cm;5cm for 4sides. --- 16:9 Size up to 240cm;25cm T and 3cm for L, R, B. ---- Size bigger than 240cm;25cm T and 5cm for L, R, B.