Several years ago I purchased a Troy-Bilt trimmer and all the attachments at Lowes. I became displeased with the performance of the engine one day when I realized that the reason the brush trimmer wouldn't cut was because the engine was running backwards.
I flew hot, said some choice words about cheap big box store equipment, drove to the nearest JD dealer and purchased a Stihl Combi head. I asked the salesrep if the Troy-Bilt attachments would work on the Stihl. He acted offended and said that the Troy-Bilt attachments would absolutely NOT work on a Stihl. I bought all the Stihl attachments while I was there.
When I got home I tried the Troy-Bilt attachments and they work perfectly on the Stihl. Taking the word of the "expert" cost me a lot of money that day. Sigh.