The MID49 Baseline Arca Dovetail is a 12mm tall Arca-Swiss standard camera dovetail. It includes a central screw slot designed to fit the provided 1/4″-20 and 3/8″-16 captive camera tie-down screws. This slot allows you to adjust the camera’s position forward or backward for improved balance. The built-in lens support clamp also enables you to attach a lens support post when using heavy lenses or lens adapters.