Spool Refill 80mm dia

A remake of the best reusable spool for refills I could find was from car7er at https://www.thingiverse.com/thing:3060389

The original design was filament and time efficient - thank you for designing it! My issue was that it was too big to fit the refills I got locally (I was trying out the refills from Matter3D here in BC, Canada), so I adjusted and made a few improvements.

- These fit spools up to 80mm inner diameter; and up to 185mm outer diameter.

- I've adjusted the screw holes to fit M4 bolts on 2 sides. I used M4x20 (2 pcs), but the nut is shallow enough that you could use M4x12 (2pcs).

- For added durability and reusability, I've created a way to inset M4 nuts. You will need to pause your print and add the nuts in manually. Screws wear out the plastic over time, so I don't trust not having a nut in there.

Room for improvement:
- I need to adjust the holes for each of the filament ends. Might update at a later date.

Hope someone else finds this version useful!