If you're looking for a good knob for your switch, you can just stop reading and order straight away.
The original knob on my guitar was very loose for a long time, and eventually fell off. I didn't look around very long until I found this one, and there wouldn't be any reason to.
It sits really tight, and also has a very nice colour that matches my guitar very well.
I was a bit too tight to fit at first, but then I let it soften for a minute in a cup of hot water, which made it easier to push into place.
Ever since that day, it's been sitting nice and tight on my guitar.
I haven't tried to pull it off, but I guess it would be easy by flicking it with pliers.