Sourcingmap 10 Pcs Black Silver Tone 16mm Top Rotary Knobs for 6mm Dia. Shaft Potentiometer

These fit perfectly on top of a KY-040 rotary encoder (6mm D-shaft). There is a little screw that holds the cap firmly in place. They are just as small as they can get to be gripped comfortably, meaning you can put multiple encoders closer to each other.

These 16mm diameter (at the widest point) are ideal if you like to make your own effects pedals. Clearly based on the Boss ones, they quite well made (although some of the metal disks needed pushing down properly), good value and arrived surprisingly quickly considering they came from the far east. They fix to the post shaft with a small grub screw.

These fit perfectly on a round 6mm potentiometer shaft. There is a little screw that holds the cap firmly in place when tightened. Excellent for DIY guitar pedal construction, which is what I've used them for.

These fit my monologue great but you have to use the locking screw to stop then going to far down or they will rub you beloved synth, others than that they look and feel mutch nicer on my opinion