Just thought I'd post this for others to see. I posted this over in the YZ/WR 250 forum, but thought I would post it here as well since it also fits the WR 450. I was just checking the Yamaha web site and found this. It's for the 05-07 WR 450 & 250 stock exhaust. http://www.yamaha-motor.com/sport/accessories/acscitemdetail/5/66/55/2301/all/1/6872/0/detail.aspx It's about time Yamaha caught up with the aftermarket world and offered this product. I guess they got tired of losing money to companies like Pro Moto Billet and Quiet Products. I've got the one from Pro Moto Billet for my WR 250 and really like it. It opens up the stock exhaust, is quiet, and much cheaper than a new exhaust.