I really liked terrago's "tush - ultimate spool" design and wanted to try it. so i added some clips to easily mount it to my wanhao duplicator i3 plus (other versions might work as well).
The spool holder consists of 2 parts instead of the original 1. One which has the clip on it and another wich clips right in when you add the 608 bearings.
I advise using a simple filament guide like this one along with it, since i noticed that the filament tends to scratch along the spool holder when not using one.
I removed the bearing rings, since i noticed it was spinning more freely without them.
Sketchup source files are included
Used 40% to make the small extra pins i added a bit more durable