I have probably printed more filament adapters than most, nothing has been quite right, either the prints take hours or they need to be printed in something more robust than PLA, so take even longer to print!  Who wants to waste time printing spool adapters just to get printing, not me, and if you are like-minded, give this one a go!

I realized that actually all we need is to transfer the push from the Elegoo spool springs into whatever filament we are trying to use, and put a flange on the end so the reel doesn't fall off all over the floor!

This is to fit filament spools of 72.8mm diameter.

I printed this in some random cheap PLA from Amazon and the print specs are <38mins total print time, less than 24g of filament!  It works beautifully, transfers some of the springing from the Elegoo spool holder right on to the inside of the larger spool.

I've designed many spool adapters myself, this is my last one (I think) as it just works and is reusable with no glue/ no tape and no cracking parts!