Progressively wound springs using Kobe super-clean, chromium silicon(CrSi) based wire that is heat treated and shot peenedTight-tolerance, FEA-designed hardened steel Posi-Loc™ style upper or titanium retainers to ensure correct assembly height and resist keeper ''pull through''Heat treated (H.T.) steel basewashers are designed to fit on top of either the OEM or KPMI tophat seals in this kitMade in the USAKit uses OEM-style valve keys (sold separately).'23-'24 CVO's check valve lift to deteremine compatibility with Kibblewhite Precision Machining Inc. (KPMI®) spring kits.