Smallrig
Accessory Thumb-Wheel-Lock-Nut-877
- Wheel Lock Nut
 - 1/4" Female thread
 - Lock Nut
 - For Maigic Arms and Ball heads
 
                    
                Thumb-Wheel-Lock-Nut-877
Thumb Wheel Lock Nut 2pcs pack
Center 1/4" screw hole
It features a standard 1/4" hole that can be used in articulating arms or shoe mounts with 1/4" screws. It is lightweight, durable and compact. 
Source: https://www.smallrig.com/smallrig-thumb-wheel-lock-nut-2pcs-pack-877.html

                

                    
