The original part seemed a bit loose, and I eventually got round to investigating. My belt measures 1.7 mm over the teeth, 1.2 mm in the teeth. Although the short section in the original looks OK, the long section is 0.5mm too wide.
The remix ix the 4mm version, with the 2nd path made narrower where the two belts overlap. The other end is slightly tighter, but relaxed a little so it doesn't push the belt sideways.
I have also split off one of the mountings to act as a retainer, and provided a small 'test fit' part which you can use to test against your belt. Both slots need to fit :)
Use either the 'simple', or 'base + fixing' parts.
First time round, i got far too tight a fit. Will wait till i have a new belt before fitting the replacement (the old belts looking a bit ragged after a year).Tweaked again 9 Oct 2017 for slightly easier fit.