These gear rings are made from flexible stretchy rubber, allowing them to be wrapped tightly around any lens focus ring and tightened using the clamping screw without the risk of slipping off or changing position during operation. 
The belts are adjustable to fit any lens diameter up to a maximum 95mm. Module 0.8 is the size of the gear tooth and is the industry standard that fits the vast majority of follow focus units including all the models we sell. 

Professional Top Quality Flexible Follow-Focus Gear Rings can be used with all lens types such as Canon, Nikon, Sony, RED etc.....

Features:

• Industry standard 0.8mm pitch, compatible with the vast majority of follow focus systems.
• Approx. 95mm Long Gear Belt works on any prime or zoom lens.
• Unique locking method to prevent slipping.

Specifications:

• Pitch Module : 0.8-125
• Maximum Diameter : 95mm
• Minimum Diameter : 20mm
• Weight : 17g
• Width : 5mm

Package Contents:

1x LanParte FFGR-01 Pro 0.8 Module Flexible​ Follow Focus Gear