This might be common knowledge, but I'll share anyway. I really wanted to improve my vent knobs, but the standard guitar knob is way too big. However, after a bit of research, I found out the top of a dual concentric knob is perfect. The original by kvis was way too long, so I recreated it. Also, this is designed for knobs with 6mm smooth bore, locked by a headless screw.
Designed to be printed on resin printers, but feel free to try FDM
Vent_knob.STL | 12.5MB |