I purchased this knob to use on my Bass Guitar that has a 3-band active eq. The Bass and Treble are controlled by a concentric pot, so I needed a knob specific to that function. The lower half of the knob fit well on the pot shaft, and the set screw engaged properly. The upper portion of the knob was too tall, and the set screw position was above the pot shaft, therefore not engaging. I as able to reduce the height of the upper portion by removing material from the bottom of the knob. This allowed the set screw to contact the shaft to lock it in place, However, the top knob once locked in place sits crooked on the shaft (the shaft is a smaller diameter than the hole in the knob. It took about 30 minutes of fiddling around to get the upper knob to sit fairly straight and not hit the lower knob when turning.While the knobs look great, I would not recommend them. I'm sure not everyone has the machine shop I have to modify the knobs so that they will be functional.