For fast transitions from tripod to shoulder rig, use this Manfrotto-Style Drop-In Baseplate from SmallRig, which is compatible with a separately available Manfrotto 501PL quick release plate. The quick release plate drops, rather than slides, into the baseplate for fast mounting and unmounting.
The sturdy aluminum baseplate features two 1/4"-20 safety screws to prevent a 501PL plate from sliding out, and it tightens with a locking lever that secures with its own quick release buckle. There are multiple 1/4"-20 and 3/8"-16 threads on the bottom of the plate for mounting options. Two Allen wrenches are included for adjusting the safety screws.
Manfrotto 501PL-style quick release plate
Rigs with 1/4"-20 and/or 3/8"-16 screw mounts