In case you, like me, happen to have 625zz bearings laying around instead of 695zz and would rather use them then buy new bearings...
Body and Cover (plus mirrored parts), opened up for 625zz bearings.
If installed from the front, the m3x10 bolt for the idler bearing will crash into the cover-side 625zz blocking the idler from putting pressure on the filament. Just install the m3x10 from the back and this problem goes away. The shorter the screw-head the better.
Also, because the 625zz bearing is 5mm thick instead of 4mm, to keep the filament aligned with your mk8 bearing, the motor-side 625zz and large gear need to be installed to be about 1mm closer to the motor and there might not be enough room to install the small gear that much deeper on the shaft (for me everything fit fine).
In case you have an issue, I included a slightly thinned down the large gear (on each side 0.5mm removed, so 1mm thinner in total), so it only moves about 0.5mm closer to the motor and the small gear only needs to be installed 0.5mm deeper on the shaft (there definitely should be room for this).
I use this with this printed groove mount adapter
and the nut from here