A large MXR-style knob. 1.5" diameter at the base of the skirt. Can be scaled to suit your own needs (the one used for guitar pedals is 1 inch at the base). There are 4 sizes of this knob that I know of: 1.5", 1.25", 1", and 0.75".
I made this one myself from scratch because I wasn't totally satisfied with the existing ones in the 3D Warehouse.
#amp #effect #guitar #knob #mxr