Weighted Shift Knob

I wanted to make a replacement shift knob for my Mazda 3. I was loosely inspired by WillsWorld's [WRX Shift Knob](https://www.thingiverse.com/thing:977220), but I wanted a shift knob that would be at least as heavy as the factory knob which weighs a little over 100g. To achieve this goal I hollowed out the middle of the shift knob to accommodate 3/8" by 1-1/4" fender washers. I also designed the knob to be 20mm shorter than the factory knob (86mm to 66mm). The shorter knob, increased weight, and tighter mounting compared to the factory shift knob greatly improve shift feel in my opinion. This knob was designed for 3rd generation Mazda 3, but may work for other cars.


Parts
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1x M10x1.25 Locknut (Some cars use M10x1.5 threads instead)
16x 3/8" x 1-1/4" fender washers (Metric washers are hard to find in the US, but 10mm x
30mm is the closest size to the one I used)
6x M3 x 16mm bolts
6x M3 Nuts

Material Selection
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From my reading th