Stens 615-078 Carburetor Kit Replaces: Zama rib-41 Fits models: Stihl: 021, 023, 025, FS300 and FS350 Zama: c1q-el21; c1q-el22; c1q-s11c-e; c1q-sp16az; c1q-w14a; c1q-el23, a; c1q-el27; c1q-w20, a; c1q-w14, a Carburetors Ethanol: not compatible with greater than 10% ethanol fuel