Replaces OEM: 4009 710 2106, 4009 710 2100, Please double check if our part number and size are what you need. This trimmer's mowing head is compatible with Stihl FSA 57 (2020 onwards), FSE 52 (2020 onwards). 2mm double nylon line mowing head, suitable for mowing and cleaning lawn edges, around trees and walls, mowing quickly and efficiently. This mowing head has a diameter of 87.5mm, and the housing has an easy-grip contour, which can easily release and fix the mowing head manually. The mowing line can be adjusted automatically by tapping the mowing head, and the cutting line can be refilled from the outside without the tedious operation of opening the housing. Part Number 4009 710 2106 4009 710 2100 Dimensions 87.5mm Diameter Line D.