FEL-PRO VALVE STEM OIL SEALS HONDA D/B/F/H/K-SERIESFel Pro engineers analyze the OE design for every application. The OE design is tested and benchmarked. Based on the analysis, we determine the material used, considering the durometer (relative hardness) of the rubber, temperature requirements (both extreme heat and extreme cold), resistance to common oil types, tear resistance and leak rate. This type of analysis makes one thing clear, not all valve stem seals are created equal. Visually, a lower