Yeah, let me explain. First, I'm an old geezer with arthritis in my left hand. This makes it painful and difficult to turn a focus knob with that hand when I'm in position. Second, when I shoot a 1000 yards match, I like to check the mirage at closer ranges and then pop back to 1000 to take the shot. This wheel makes is super easy to do that, just crank back a certain amount and then crank it back to the proper setting in an instant.Good grief. If you need that to focus, better find a different scope
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You can get the middle wheel that fits your focus knob and that's the one I have on my March 1.5-15X42 as you can see in the picture earlier. On my March-X 10-60X56 HM on my F-TR match rifle, I have the middle wheel and on top of it I have the 3.5inch large wheel.
This works well for me and I know of other people who use only the middle wheel and like the fact the focus adjustment is more granular with the larger control.
You don't have to have one on your scope if you don't want it.