I used a CR 500 pipe that I welded the kx neck to. You have to do a little "adjustments" with your hammer, but it fits pretty nicely. If you want an existing pipe, the Service Honda pipe has been used on a couple of guys projects. The pipe on Toby's bike looks like an FMF pipe made for the K5 that allowed you to use a special larger tank. Notice how it goes over the shock reservoir like on a 500. Motorrad has one on his bike.