STIHL O-Ring 25 x 3.5 - Genuine OEM Seal Ring The STIHL O-Ring 25 x 3.5 is a genuine OEM sealing ring designed to provide reliable leak protection in small engine assemblies, fuel systems and fluid connections across a wide range of STIHL outdoor power equipment. Manufactured from durable rubber compound material, this O-ring helps maintain dependable sealing performance under exposure to fuel, oil, vibration and temperature changes commonly found in professional and domestic handheld machinery. With a precise 25 mm inner diameter and 3.5 mm cross-section, the STIHL O-Ring 25x3.5 fits accurately into matching grooves to support consistent sealing without distortion. The exact dimensions of 25 mm x 3.5 mm help maintain proper pressure retention in housings, caps, carburettor interfaces and line joints. Suitable for equipment including the STIHL FS 40, FS 40 C, MS 261, MS 500i and BR 600, this genuine seal ring helps reduce leaks, supports smoother engine operation and assists with long-term reliability during routine servicing and repairs. Key Features Genuine STIHL OEM O-ring for assured fit and sealing performance Size: 25 mm inner diameter x 3.5 mm cross-section Durable rubber construction designed for engine and fuel system environments Helps prevent fuel, oil and air leaks in compatible assemblies Supports reliable starting and smooth engine operation Resistant to vibration, heat and outdoor operating conditions Accurate dimensions for dependable groove fitment and sealing integrity Suitable for chainsaws, trimmers, blowers, hedge trimmers and Kombi tools Useful replacement during servicing and preventative maintenance Designed for repeatable OEM-quality sealing performance Typical Applications This STIHL O-ring is commonly used to seal static and lightly dynamic joints in small engines and handheld outdoor power equipment. Typical uses include fuel system joints, carburettor interfaces, line unions, housing seals, pump seals and cover assemblies where reliable sealing is required to prevent leakage and maintain correct system pressure. The 25 mm inner diameter and 3.5 mm profile make this seal suitable for many STIHL brushcutters, chainsaws, hedge trimmers, Kombi tools, blowers and cut-off machines operating in forestry, landscaping, grounds maintenance and domestic garden care applications. Technical Specification Brand STIHL Product Type O-Ring / Seal Ring Size 25 mm x 3.5 mm Inner Diameter 25 mm Cross-Section 3.5 mm Material Durable rubber sealing compound Manufacturer Part Number 9645 948 7734 Alternate Part Numbers 9645-948-7734, 96459487734 Fits Models Compatible with a wide range of STIHL equipment, including selected: STIHL FS 40 & FS 40 C brushcutters STIHL FS 56, FS 70 and FS 90 series trimmers STIHL KM KombiSystem engines STIHL BR 500, BR 550 and BR 600 blowers STIHL MS 171, MS 181, MS 261 and MS 500i chainsaws STIHL HS hedge trimmers STIHL HT pole pruners Additional compatible STIHL models listed in manufacturer parts documentation Also Known As Seal ring Rubber sealing ring Circular gasket Round-section seal O-ring seal Ring gasket Fuel system O-ring Why Choose Genuine STIHL Seals? Small sealing components play an important role in engine reliability and pressure retention. Genuine STIHL O-rings are manufactured to precise OEM tolerances, helping maintain the correct fit, compression and chemical resistance required for outdoor power equipment exposed to fuel, oil, vibration and varying operating temperatures. Complete Your Kit STIHL Spare Parts 2 Stroke Oil Chainsaw Files Fuel & Oil Cans Explore More Chainsaw Accessories Brushcutter Heads & Blades Hedge Trimmer Accessories Blower Accessories FAQs What size is this STIHL O-ring? This O-ring has a 25 mm inner diameter and a 3.5 mm cross-section. What is this O-ring used for? It is used to seal fuel, oil and air connections in compatible STIHL outdoor power equipment. Is this a genuine STIHL part? Yes, this is a genuine STIHL OEM sealing ring designed for compatible STIHL machines. Which STIHL tools can use this O-ring? It fits a wide range of STIHL chainsaws, trimmers, hedge trimmers, blowers and Kombi tools. Why replace a worn O-ring? Replacing damaged O-rings helps prevent leaks, maintain pressure and support reliable engine performance.
