Just finished new build and wanted to have nice black knobs with great grip. Especially that I've been using push-pull pots with switches. 
Without thinking too much, I pushed those knobs on my pots. After 10 seconds decided I do no like the optics, so started to pull them out. Finished with two damages DiMarzio pots (with switches). 
 
So... 
PROS first: 
- The grip is really fantastic 
- Optics not bad 
- Clearly visible numbers (very useful if you use eyes instead of ears to set volume) 
 
CONS 
- Fit. it is so tight, that once on pots, it is virtually impossible to take them off without damaging pots. 
 
CONCLUSION 
Nice knobs, great idea for very good grip, very usable, when you have push/pull potentiometers with switches. 
I am using them, and probably will continue using and slowly replace my old Fender style knobs for this ones. 
But now I am wiser, and before fitting them on guitar, I am redialling the hole, so the fit is tight, but not insanely tight, like them come originally. 
 
3 stars total, as those knobs can cause potential damage to your guitar due to non-standard shaft hole.