RFX Pro Engine Timing Plug Set - Blue FXEP6010099BUPro Series Engine Timing Plugs RFX Pro Series Engine Timing Plugs are manufactured from 7075 T6 aluminium for increased dimensional stability under high heat and pressure conditions. CNC machining for tighter manufacturing tolerances helps these plugs stay in place over standard plastic plugs which are prone to failing. RFX Engine plugs also feature handy 8mm and 6mm hex key heads for easier installation. Features 7075 T6 Aluminium Construction. 8mm