Extruder Knob/Valve/Wheel.

thingiverse

I love the original design, but it's slightly too large for comfortable use on my Ender 3 with the Z-screw so close, and it looks quite sharp and crude without chamfers on its edges. So, I decided to brush up on my Fusion 360 skills and recreate the design with the tweaks I wanted. I ended up with three variants: the largest is 40mm, the medium one is 35mm, and the smallest is 30mm. The hole is supposed to be tapered for a good push fit, but it's quite tricky at these sizes as even the tiniest amount of over-extrusion or under-extrusion will mess it up. If needed though, it's a good thing these are small so scaling and reprinting won't waste much. Fusion 360 project files included, once Thingiverse decides to display them.