This is the Needle Vavle O-ring for the FS/FX/LA OS Max series engines. FEATURES: Silicone construction. INCLUDES: Two O-rings. SPECS: Outside diameter: 6mm Inside diameter: 2.5mm Thickness: 1.5mm COMMENTS: Can be used for other applications where a 2.5x6mm silicone o-ring is called for. NNA 2/13/02