3d printed threads and snap connectors are nice, but M3 bolts and nuts are more robust and look dope. They also make the model easier todesign print, since you don’t have to worry about tolerances as much.
STEP/STL and instructions available here: www.printables.com/model/548770-master-spool
They = quite a few brands so far. The ones I know of include microcenter (inland), fiberlogy, sunlu, and esun. I’m not sure how many are interchangeable but they sell the refills wound onto a cardboard tube/core with a few straps keeping the winds from falling to the side since there are no spool sides to keep it in place. You slot the cardboard core onto your reusable spool sides and once attached you can cut the straps to release the filament.
So you have to do all this instead of having 2 cardboard circles on the side of the spool. 2 recyclable circles
I think it’s more of a replacement for plastic spools, since cardboard doesn’t work well in edge roller spool holders and master spools are almost always reusable plastic which does work in edge roller spool holders. If your spool holders work with cardboard rims then yeah there isn’t much of a reason.
I like formfutura filament. Their refills cost like 20 moneys per kg (PLA). Their easyFil PLA is 40. Their brand has the biggest price difference. Usually the difference is up to 5. So still savings.