This is a genuine Stihl air filter p/n 4140 124 2800, which fits the FS55, FS55C, FS55R, FS55RC, FS55T, KM55, KM55C, KM55R, KM55RC, FS38, FS45, FS45C, FS45L, FS46, FS46C, HS45, FC55, FC55, HL45 & many other machines. If you are unsure whether this is the correct part for your machine, please fill out our online parts enquiry form here. The technical department will then respond to confirm whether or not it is the correct part for your machine.