i just don't realize what that is for. is it so that if you have to have like a "bowtie" fitting blade, the adaptor will allow you to "adapt" it to be able to use like a circle fitting blade instead? i have a 21" Troy-Bilt and it has the bowtie with the two circles on each side of it. just wondering if the adaptor kit is something that would allow me to, let's say, get a mulching blade for it that has the circle in the center of the blade. if that is correct, could i use a John Deere mulching blade on it?