aoa. Sorry for maybe one of the most delayed reply on Pakwheels but i m not much active anymore cause of the routine. well bro the center bulb in stock city is NOT double filament. It only lights up with parking light and goes off when u turn the light off. It has nothing to do with brake. Therefore, it stays single filament. The outer most is by default double filament for more light on braking. I have installed double filament on both outside and inside of the car with the arrangement that on parking light only their ONE filament is on, and middle bulb (the single filament one) is off. when brake is applied, the second filament of side bulbs and the lone filament of center bulb lights up 