Swenor's smallest classic wheel at 65x40 mm. For the front. This is free spinning both directions.

Total width of hub with wheel spacers is 44.7mm. Hub is 34.2 mm wide, and each wheel spacer is 5.25mm. 

You can put these on Elpex Evolution V classic rollerskis instead of Elpex 70x40 wheels. Reduces ground clearance a little, but when installing on Elpex, reuse your Elpex wheel spacers as those are 5mm thick and hubs same width.