This is a variant on emmett's PrintrBot Spool Holder, which I really like a lot. It's the best spool holder I've seen, as integrates onto the printer securely without dangling the spool off the side, which can interfere with high-Z builds. I used it for several months until it broke when my PrintrBot fell over during transport in my car. Before printing a new one, I made these mods: Print with decent fill for strength. You may have to rotate this slightly in Cura to fit on the PrintrBot platform.