Found 7 mln. answers for '608'.
https://www.epa.gov/section608
https://www.epa.gov/section608/section-608-technician-certification
https://www.epa.gov/section608/section-608-technician-certification-0
https://www.youtube.com/watch?v=sLXafheMO3U
https://www.amazon.com/slp/608-bearings/yzmzownyb82e8k3
https://www.amazon.com/Skateboard-Bearings-Double-Shielded-Silver/dp/B002BBGTK6
https://www.amazon.com/608-2rs-Premium-Bearing-Bearings-ABEC3/dp/B009Y9IRNA