This is for the injected molded spool holder not the 3D printed one.

If you have ever tried to install a spool holder on a Prusa XL, you know it can be frustrating. Getting the screw to find the hole is the first problem, then trying to get the allen key into the screw head is maddening.

This simple part fixes those problems. If installing the spool holder for the first time, position the holder with the open side up. Drop the helper, flat side down, into the holder. Make sure it is all the way down. Now drop the screw, thread side first into the holder. It should just drop through the hole at the bottom. If not, just wiggle the holder a little until it drops into position. Now using the 3mm allen key, insert it all the way into the holder rotating it slightly until it aligns with the screw head. You'll feel it snap into place. Now, holding the allen key and holder together, align the screw with the M4nEs nut in the extrusion and tighten.

If you want to remove or reposition a spool holder, insert the helper, flat side first. Use the allen key to push it all the way into holder. Now using the 3mm allen key, insert it all the way into the holder rotating it slightly until it aligns with the screw head. You'll feel it snap into place. 

Make one for each spool holder. PLA or PETG work fine.