Just look for the welded bead all the way around the muffler canister near the first 1/3 of the total length. That will tell you if it's for the YZ450F. Also the YZ450F GYTR muffler P/N GYT-2S293-01-TT has the pipe diameter stepped up at the forward end and can't be used with the stock head pipe. You will need to buy head pipe P/N GYT-2S293-50-10 to make it work. Yamaha GYTR Titanium Exhaust Muffler YZ450F - NEW !! GYT-2S293-01-TT Fits '06 06-08 YZ450F GYTR Replacement Muffler, Titanium/Aluminum ***(Does not fit stock head pipe)*** P/N GYT-2S293-01-TT 06 YZ250F GYTR Titanium/Aluminum Oval Muffler P/N GYT-5XC93-01-TT I spoke to the guy and he told me he would refund my $ 100%. I told him I will be sending it back but to be honest its a big hassle. I would love to think it will work and just use it considering it fit. But Grey you say it could be shorter and effect performance. I did buy that after market head pipe assuming I would need it. I am not able to return that either so I will be out that money too. Is there some way to know if its a 250f muffler for sure? Sorry if I missed that. I know you told me to look at the welds speedracer but its bolted on so im sure its not the one you showed me in the above pics. I think thats the muffler I was hoping to get.