I read that some guitars take a recessed skirt knob of they stick up like a mushroom...
Another consideration when choosing a knob for a Gibson Les Paul® is whether you want vintage style non-recessed knob. Guitars fitted with this style of knobs will look like the knobs are not pressed on all the way. They can sit anywhere between 1/8″ to 1/4″ above the guitar body. These are found on a lot of vintage Gibson guitars and also their historic line of guitars. On some guitars the knob can look like it is sitting way too high and will need the control lowered to make it look better. This can be difficult to do on some guitars(ie. Gibson guitars with the PCB). Here are some examples on a Gibson Historic and a 2010 Gibson Traditional with non-recessed knobs installed.