A spool roller/idler which is easily ("OTED") adjusted to spool widths from about 50mm to 125mm. In the blender file attached, just modify the frame for a different range to your liking or needs.I never found a spool idler fitting my 2.3 kg spools from ReprapWorld, and I was never certain that I would get those spools again. So, I mocked up this design where the 608-guides in one side are confined while the 608-guides on the other side may slide freely on the axles in a wide range.The frame is not too nice, and warps easily for me. I will probably make a new design which should print faster, warp less (rounded corners), and use less material. However, for now this one works very fine.(Note: OTED, One Touch Exchange of Die, came out of development towards just-in-time production control at Toyota by a really smart guy, Shigeo Shingo. If interested in flexible manufacturing go for his book "A Study of the Toyota Production System", ISBN 0-915299-17-8. Or just get some interesting information at http://en.wikipedia.org/wiki/OTED)Print or get two 150mm long 8mm smooth rods. Print one frame. Print four "608 belt guides". Print eight spacers.Aditionally you need four standard 608 bearings, and, if you did not print them, two 150mm long 8mm smooth rods.N.B.: The "608 belt guides" should have a very snug fit to the bearing. Hence, you may have to adjust the size in the .blend- file or scale the stl to fit your mis-calibration.Assembly is straight forward. The smooth rods should have stickout enough to mount a standard clamp, but it is not necessary.