I knew they exist when I bought a Boron 2 from Yonex. There was also a Boron 3 and a Boron 7, but exclusive to Japan. Last Friday, there were some 'older' players at our place. They had a very good technique, but there back were playing parts. So I discovered they played with some older rackets and when it got my attention, he showed a racket in his bag I never saw before. Not even on pictures! It was a Boron 7 from Yonex. He had 3 of them, but this was the only one left. Not in perfect condition, or I would made him an offer.