The PA-100 is a 100mm Systematic-compatible flat plate that mounts to the Atlas series tripods. It features a hook, three set screws, a 3/8" mounting screw, and is fully compatible with 100mm Systematic tripods from other brands. Pops on and pops off the tripod quickly and easily, so if you use several heads, having multiple PA-100 units allows you to switch between heads securely in seconds.