APE retainers are fully CNC machined from aircraft quality Titanium bar. Titanium retainers are many times stronger that OEM aluminum retainers and should be used whenever valve spring pressure is increased. Hayabusa (Set of 16 retainers) GSX-R1000 01-04 (4mm stem steel valves) GSX-R1000 05-08 (4.5mm stem titanium valves)
