This extruder lever arm perfectly fits the stock extruder of the monoprice select mini with the only additional part being a 5x11x4 bearing which is readily available locally/online in hobby shops as it is one of the most common rc car bearings (traxxas 5116). The main advantage is the MUCH thicker stronger bearing spindle (5mm vs 2-3mm of the original lever arm).
Installing this arm simply requires the original m3 hex axle bolt and bushing of the original extruder and dropping on the bearing. I originally intended to have a press fit 'cap' over the bearing, but as it turns out the bearing has no tendency to wander upwards anyway.
NOTE : the input hole in the arm has been sized to 4mm ID so that if you wish, you can easily attach/glue/pass through a length of 4mm OD ptfe tubing.