Sometimes parts go missing or need replacement. Keep your Streamlight flashlight in top working condition with authentic OEM factory parts. The Streamlight Face Cap Head O-Ring fits any Streamlight SL-15X, SL-20X, SL-20X LED, SL-20XP, SL-20XP LED, SL-35X Flashlights. Don't get caught in the dark, keep shining on with Streamlight replacement parts.