These are knobs to slip on to the low and high fuel adjustment knobs to Ryobi(and others) Carburetor. I used a Ryobi R09050 blower for testing and fabrication. I also included the blend file that I created the peices so you can modify in any way you see fit. I reccomend a 0.4mm nozzle as the shank thickness is 0.4mm. The knob is chamfered on the key side so you can see the index of the adjustment. I recommend marking this part of the knob with a Sharpie or similar. I also have a tool for adjusting the carburetor available here: https://www.thingiverse.com/thing:5574224