Modified V-slot wheels!

Made a complete redraw of the original in 123D, optimized for printing WITHOUT supports and made a smaller version for 12 mm OD bearings.

Any type of filament will be good for printing these - ABS, PLA, Nylon, Flex...
Use Flexible filament if you want silent wheels and ABS if you need stiffness

*** Important ***
In your slicer set layer start points to RANDOM. Otherwise, a bump will be formed on one side of the wheels and they will not roll well.