Rotary encoder knobs exist in several shapes and sizes, yet it's hard to find a knob that has the right dimensions to fit on a keyboard with the common 19.05mm key spacing.
This is why Thomas Baart (of SplitKB.com) designed his own knob: 20mm in height, 19mm in diameter at the rim, and a 18mm body diameter. This knob is designed for rotary encoders with a 6mm flat shaft, much like the common EC11 encoders, and sits lower to the plate than most knobs, closing the gap and making for a lower profile.
The matte finish prevents fingerprints from showing up, while the knurl on the side provides ample grip to easily turn the knob. The slightly rounded edges make it comfortable to the touch.
The knob's set screw requires a 1.5mm Allen key. This is included with the knob.
The keyboard and keycaps shown are not included with this item.