Even though the information about the Orbitrim Pro said it would be compatible with my Ryobi gas trimmer, none of the bolts that came with it would affix to its female bolt end. I went to several stores trying to find a bolt that would work, but try finding a one inch long 8mm hex head that is 9/16 and is a left turning bolt with fine threading.
The Ryobi attachment bolt has a courser thread than the ones in the package. Unfortunately, it has a pentagon head, so it will not work with the Orbitrim. I called the Orbitrim company and they only have the 5 bolts that they sent me, so they couldn't send me a bolt that would connect the Orbitrim to my Ryobi. They said they would have a tech guy call me, but I never got a call.
I wasted a lot of time trying to get it attached. Now I have to repackage it, drive back to the store and go through customer service at Menards and show my sales receipt, then go back home and reattach my old Ryobi string trimmer head.
Bottom Line: No, I would not recommend this to a friend