A mounting system for a bicycle light, camera, bike computer, smartphone or other device has versatile application to front or rear of the bike, to fix the light or device in position at the desired orientation. The mounting system has a ball arm engaged by adjustable clamps, one on each of two ball ends of the ball arm, providing a wide range of adjustments to attach the light housing or device to different configurations of bicycle stems and to seat rails below the seat, accommodating a range of different spacings and angles.