The can comes with its own check valves, the Billet Pro Series Valves are just slightly higher quality. The same goes with the PCV fitting, which is included. UPR's High-Flo fitting is just a bit better quality and arguably flows better than the base fittings. Frankly, we think most of UPR's options are a but superfluous, and the base can with its standard hardware works perfectly well on 99.9% of trucks and applications.