Rotary 15875 Air Filter replaces Stihl 4144-124-2800. Fits models FS40, FS50, FS56, FS70, KM56, HT56. 

Replaces
STIHL: 4144-124-2800, 4144 124 2800
Fits Models
STIHL: FS40, FS50, FS56, FS70, HT56, KM56

Dimensions and Specifications
THICKNESS 1/4"
WIDTH 2-3/8"
LENGTH 3"

SR-2