The medium-size CatLABS TAAB Lens Focus Tab fits 50 - 64mm lens diameters and helps you achieve fine focus control. It has an unobtrusive and compact design that becomes part of your lens. A rigid finger tab provides control when focusing for a smooth and tactile feel.
The aforementioned lens is available with a focus tab in the more expensive M mount variant, while the other variants do not. As I would like a focusing tab for this lens, this was essentially the only option from B&H which was not adhesive. It works quite well: the number of teeth in the band almost match the number of grooves in the focusing ring on the lens, and it's a tight fit. The two downsides are that it can slide up and down the barrel (rubber on metal, of course) and that the band which I received is not solid black, but rather a marmorated gray with black mixed in. I initially thought this was some issue with the rubber, but it is indeed the way it is pigmented.