I'm a huge fan of the steering wheel knob on my tractor, however the one pictured by the OP didn't work on my B2601. Instead, I opted for a slightly different style like this:
One New Aftermarket Replacement Orange Steering Wheel Spinner that fits Various Tractor ModelsReplaces Part Number: WSV125OR Aluminum Knob with Protective Orange Vinyl Coating Sealed Ball Bearings For Shallow or Deep Steering Wheels Weather Resistant
www.reliableaftermarketparts.com
I found that they type shown by the OP would not fit the wheel spoke on my B2601 (the knob goes on the spoke, not the outer ring). The style I installed, specifically designed, works awesome.
98 1/2% of the time I'm steering my tractor, my left hand is on the knob. It doesn't return to the same spot each use (see post above) but it is still very useful and handy. However, it is an area to be respected, as the poster above mentioned with his carpenter pants loop.
Edit: I also have 'tilt steering', used regularly; great for getting on/off the tractor.