These durable knobs come with a set screw and are built for 1/4" shafts.
The metal top continues down to slide on your shaft. A black metal hex set screw holds everything firmly in place. The plastic is a skirt on the outside.
Not only do they work on pedals but on amps and guitars too.
They fit like a glove on 1/4" smooth shaft pots.
They've got a set screw. Slide them on your pots and tighten gingerly.
WxH= 19.5 x 15.7mm