Superbrightleds 1157-R18-T. You must match the LED color to the lens color, in this case, red. This is not a cheap item - I paid $40 bucks (including shipping) for two of these - they are worth every penny, noticeably brighter than incandescent and cheapo LEDs. Also, they are designed to emit light around their circumference, not just to the rear, so good for side visibility.