A focus tab can help you focus faster in two ways:
1.- The ring becomes much easier to turn and control.
2.- The tactile feel and position of the tab will aid you (without looking) in knowing what distance is set on the lens. For example at 1500 (3:00pm) it will be exactly at lets say 3 meters and at 7:00pm it would be at 1 meter. Since this TAAB is movable, you can set that distance to your liking.
All my rangefinder lenses have a focusing tab from original design and done in the manufacturing process, so they are fixed which in many ways is much better.
The Leica Elmarit M 90mm f/2.8 doesn’t have a focus tab. It has a long throw, which can be good for a lens like this since you need very precise movements to focus at 90mm but adding this little TAAB suddenly your motion is smother, has a better grip and has the same idea of the tabs found in other lenses.
The material is made of strong, durable and yet soft to the touch plastic. Very “grippy”
I don’t work for these guys and I had to purchase mine but go ahead and Get yours here you won’t regret it.