From Manufacturer
The Acratech Ultimate Ball Head With QR Locking Lever Clamp is the result of innovative design, created for combining low mass with incredible stopping power. With the included Quick Release Locking Lever Clamp, it's an ideal head for those who don't require the progressive tension control of the heavier (and more expensive) Arca-Swiss B1. The satin black anodized finish and engraved degree markings contribute to the solid precision look and feel of this impressive camera support. The ball operates without oil or grease, so it will not attract or hold dirt and debris. The knobs are all secured so that they can't vibrate loose and fall off.
The innovative design of the Acratech gives the photographer full access to 25% of a sphere at any time, and it is entirely capable of providing support in any direction so long as the tripod legs are not overwhelmed. This version of the V2 includes a built-in spirit level aiding in tripod and camera alignment.