This replacement piston ring is made of highly optimised cast iron that provides exceptional wear resistance and stability at high temperatures inside the cylinder. As a reliable alternative to the original part, it successfully maintains maximum compression, prevents combustion gases from passing into the housing and ensures proper heat transfer from the piston to the cylinder walls. The thin 1.2 mm construction directly reduces the friction coefficient, easing engine operation at high revolutions and extending the working life of the whole assembly. Ring diameter: 40 mm Ring thickness: 1.2 mm Manufacturer: high-compatibility aftermarket part Reference OEM numbers: 1139 034 3000, 4147 034 3003, 4180 034 3000, 1123 034 3005 Compatible models: Chainsaws: STIHL 021, 023, 023 L, MS 211, MS 211 C-BE, MS 230 Trimmers and brush cutters: STIHL FS 100, FS 250, FS 350, FS 360 C-E (type 4147), FS 400-K, FR 350 Dedicated engines and edge trimmers: STIHL FC 100, FC 110 (for 40 mm engines) Before fitting a new ring, thoroughly clean the groove on the piston of burnt two-stroke oil residue, soot and carbon deposits so that the ring has free movement and can seal properly. The ring material is brittle, so fit it carefully and without excessive spreading so that it does not break when passing over the piston crown. Before inserting the piston into the cylinder, lightly oil the inside of the cylinder and the ring itself with clean two-stroke oil for a safe first start. Stock and availability of parts can be checked by sending an inquiry or by calling our phone number.