Carburetor Carb Fits STIHL Backpack Blowers SR340 SR400 SR420 BR340 BR400 BR420, 4203 120 0601, 4203 120 0603, 4203 120 0605, 4203 120 0607 & Walbro HD-4A HD-4B HD-13B Aftermarket replacement non-original carburetor. Fits STIHL backpack blowers: SR340, SR400, SR420, BR340, BR400 & BR420. Replaces STIHL OEM parts: 4203 120 0601, 4203 120 0603, 4203 120 0605, 4203 120 0607 & Walbro HD-4A HD-4B HD-13B.