 The poppet valve's previous problems with sealing and wear had been remedied by the use of better materials and the inertia problems with the use of large valves were reduced by using several smaller valves instead, giving increased flow area and reduced mass, and the exhaust valve hot spot by Sodium-cooled valves.Up to that point, the single sleeve valve had won every contest against the poppet valve in comparison of power to displacement.The difficulty of Nitride hardening, then finish-grinding the sleeve valve for truing the circularity, may have been a factor in its lack of more commercial applications.