The used CineMilled PRO Dovetail for the Freefly MoVI Pro is designed to replace the dovetail plate that comes with the MoVI Pro to allow you to counterbalance front-heavy loads.
It is longer and offers a series of 3/8"-16 threaded holes across the back that support optional CineMilled counterweights (CM-070 and CM-080), which are available in 1 and 2" sizes and are stackable.
The plate is T-shaped, so you can mount the weights offset in cases where that would better balance the camera. It also provides holes on the sides, so you can attach the weights in a way that would let you achieve tilt clearance.
The original MoVI Pro plate comes with a countersunk screw and matching slots, but this one features a standard slotted design that supports standard tripod screws. The advantage is that a standard screw is easily replaceable if lost on the set.
Just like the original plate, the PRO Dovetail also provides the threaded mounting points on the front for attaching the rod support bracket that comes with the MoVI Pro.