Really Right Stuff's biggest ball head, the BH-55 is beautifully made and finished from high-quality steel and aluminum, with a load capacity of 22kg. This BH-55 is in excellent cosmetic condition, with a few surface scuffs near its base. Ball lock is almost criminally effective, pan action on base and clamp is smooth. A fantastic large ball head suitable for nearly anything you might be able to throw at it. Base fitting is a standard 3/8" thread; base diameter is approximately 72mm.