I have this focus gear that has never been used. I bought it new immediately after "winning" an ebay auction for a Nokton 42.5 that the seller reneged on. New in box and never been fitted to a lens. You can search Ebay or websites for followfocusgear.com to read about these gears. Here is the maker's info:
"Seamless focus gear that's designed to fit the Voigtlander 42.5mm f/.95 Nokton MFT lens. It's specially made to exactly fit the profile of the focus ring. The gears are designed specifically to fit this lens and is compatible with any standard 0.8 Module follow focus. The gear is made to the exact size of the focus ring of the lens, just tight enough to turn the focus ring without slipping so there is no need for straps, buckles, or clamps and you can take advantage of all 360º of the focus gear. The gears are rigid and sit 3-6mm high off the focus ring of your lens for a clean, low profile gear that slides smoothly onto your lens and into your current lens case. The gears do not have to be removed after each use although you can if you like, saving you valuable time when assembling or breaking down your rig. "
I have a Voigtlander Nokton (17.5) with one of these brand of gears and they fit that scalloped focus ring perfectly and don't slip.
They cost $35 + shipping new. Will sell for 20 bucks, free shipping.
"Seamless focus gear that's designed to fit the Voigtlander 42.5mm f/.95 Nokton MFT lens. It's specially made to exactly fit the profile of the focus ring. The gears are designed specifically to fit this lens and is compatible with any standard 0.8 Module follow focus. The gear is made to the exact size of the focus ring of the lens, just tight enough to turn the focus ring without slipping so there is no need for straps, buckles, or clamps and you can take advantage of all 360º of the focus gear. The gears are rigid and sit 3-6mm high off the focus ring of your lens for a clean, low profile gear that slides smoothly onto your lens and into your current lens case. The gears do not have to be removed after each use although you can if you like, saving you valuable time when assembling or breaking down your rig. "
I have a Voigtlander Nokton (17.5) with one of these brand of gears and they fit that scalloped focus ring perfectly and don't slip.
They cost $35 + shipping new. Will sell for 20 bucks, free shipping.