bought the pivot trim to replace the head of my ryobi ss30 weed wacker because I couldn't find a replacement reverse thread bolt at the hardware store. Installed it eaxactly as stated in the instructions. The pivotrim looked like a good upgrade. Used it for slightly less than 2 hours, the head had heated up due to friction and got deformed and the head slipped over the retaining bolt on the the head sending the head flying scraping me in the face when it flew by. Maybe it installs better on other makes of trimmers but the ryobi installation is pretty iffy. I would beware of using this longer than 30-40 minutes at a time without letting it cool down. Tried to go online to post on their website all I got was a phone number no one answered.