This is a derivative of ConcreteTurtle's reel holder, which is a derivative LawrenceJohnson's reel holder, designed to fit wider and even smaller diameter PLA reels (92mm wide x 32mm ID). Motivated by a spool that I bought on Amazon (listed as Jet - PLA (3mm, Orange color, 1.0kg =2.204lbs) Filament on Spool for 3D Printer MakerBot, RepRap, MakerGear, Ultimaker and UP!) that had a small diameter bore. Note: reducing the reel_radius parameter in the SCAD file below 32/2 caused OpenSCAD to crash on rendering, so this is the smallest reel radius possible without redesigning the assembly.1) Print two arms, one holder, and one end. I used Cura 12.07 default parameters when I printered ConcreteTurtle's 37mm reel version.2) Place arms in bracket on back of Ultimaker.3) Place holder on arms with larger radius section in notches nearest the back of the Ultimaker.4) Place reel on holder.5) Place end piece in notches at end of arms.When I print this piece and confirm everything works, I'll put up a picture of the new assembly...