Finally able to find a 7" Concentric for my Impact from the big K...When it arrived, the box had the right label - IM18C - and the scan code on the coil had the same, but the sticker says Makro Racer. As the Racer is a single frequency, I'm worried they aren't interchangeable. Called Kellyco - no luck on a definitive answer - I was told to 'try it and see if it works'...Emailed Nokta but no response yet - any ideas?