This STIHL BUMP HEAD KNOB is a high-quality replacement part for your trimmer. It is designed to fit AUTO-CUT 20-22 and 21-22 models and is made with durable materials that ensure long-lasting performance. This item is perfect for those who need to replace their trimmer's head cap due to wear and tear or damage. The STIHL FS36 FS40 FS55 FS66 FS72 FS76 FS81 FS86 FS96 FS106 models are all compatible with this BUMP HEAD KNOB, which makes it an ideal choice for those who need to replace their trimmer's head cap. This item is easy to install and will provide your trimmer with a smooth and efficient cutting experience.