Prusa i3 Mk2 Spool Holder Fix

I got tired of our filament spool falling off our Prusa i3 Mk2. At the same time, I did not want to go through the complexity of some of the great solutions on Thingiverse. I needed a simple, reliable fix, that printed in a short period of time and did the job.

And here it is... It leverages the standard spool holders, fits right on top of them, and prevents the spool from falling off. . The small radius of the holder does not generate a lot of friction, so you should be in for a smooth ride.