Spool Hub Spacer

These are designed to thread onto the hub from [Vincent Groenhuis](https://www.thingiverse.com/VincentGroenhuis)'s [Universal Auto-Rewind Spool Holder](https://www.thingiverse.com/thing:3338467). By placing one on the hub before your spool you can keep the spool centered more easily. A second one can be used to improve the stability of wide spools, or in some cases, as a nut to hold the spool in place!

For example, the 89mm version is sized to go inside the WIDE half of a spool from ProtoParadigm. I thread that on first and put it almost all the way to the end of the hub. then slide the spool on and finally tighten it down with a curved nut. Or if the filament is spooled on in the opposite direction, you can place a smaller 52mm centering ring on first, then the narrow side of the spool and finally spin an 89mm spacer on following it to center the wider portion of the spool. While I have successfully followed that with an XL Curved nut from the original project, it only barely grabs