Cordless brush cutter 9 inches

That’s a very specific size! A 9-inch cordless brush cutter typically refers to the cutting diameter when using a metal brush blade, though many models designed for residential or light commercial use might use a slightly larger diameter for their string trimmer function (often $12$ to $17$ inches). A $9$-inch blade is a common size for brush clearing attachments, which are swapped out for the string trimmer head to cut through thicker, woody material.