I didn't like the stock knobs on the Neptune 4, so I designed an alternative. This knob is 10mm larger and has a knurled texture for a better grip. Instead of using a threaded insert, I opted for a M3 nut. Just press in the M3 nut from the flat side of the knob and use a M3x20mm screw on the other side to pull the nut into position. The knob can be used for both the X and Y tensioners.