The STIHL FS 91 R is a commercial-grade gas string trimmer with a 16.5-inch cutting swath. It features a fuel-efficient, low-emission engine that delivers high torque for cutting thick weeds and dense overgrowth. A solid-steel drive shaft and lightweight, corrosion-resistant polymer housing provide durability for daily professional use.

The trimmer includes an ergonomic loop handle for maneuverability in tight spaces and on slopes. A multi-point anti-vibration system reduces operator fatigue during extended operation. The large-baffle muffler incorporates a spark-arrestor screen for safer use near dry brush, and a simplified starting routine with heavy-duty air filtration extends maintenance intervals.