Crower Springs and Retainers are among some of the best for the 4G63 engines. The retainers and springs fit great every time. The retainers are titanium for super strength and lightweight for high revving applications! This spring and retainer kit works great when your looking to upgrade cams or up the rev's on your 4G63!They offer tried and true Crower quality and are endlessly stronger than stock. The retainer is also titanium and for those of you who don't know, that makes them a lot lighter allowing the engine to turn even more RPM's safely.