Double line mowing head, for mowing and thinning work. Mowing lines are automatically extended when the mowing head is tapped on the ground. Compatible with 1.6 mm and 2.0 mm mowing line.  Can be fitted to the following machines: FSA 57 FSE 52 STIHL professional tip – to get the most from your mowing line, we recommend popping it in a bucket of water for 12-24 hours before using it to make it more flexible and less likely to break.