42 percent lighter than OEM steel retainers. Pair with Tuner Series or Pro Series Valve Springs for the ultimate valvetrain. Please note: When using Skunk2 Titanium Retainers (P/N 308-05-0410) on 2004 and newer engines, pre-2004 keepers (cotters) must be used (Honda P/N 14781-PR7-A01). Pre-2004 keepers can be identified by the absence of marks along the top edge (2004 and newer keepers feature laser-etched marks along the top edge). Use of improper retainers and/or keepers may result in potential engine damage.