PLA, ABS, Nylon. whatever you want. Bearings on ebay. https://www.ebay.com/itm/10-pcs-of-F623ZZ-Flanged-Ball-Bearings-3mm-x-10mm-x-4mm/142233615367?epid=2176216766&hash=item211dc8bc07:g:4KsAAOSwZQRYWqAQ