If you need to fabricate an exhaust header or intake system with tight bends, these 360 degree stainless steel donuts are an excellent way to start. Just cut the donut into whatever angles you need and weld the tubing pieces into the desired shape.*
The 1.75" through 2.25" sizes are 16 gauge thickness. 2.5" through 4" sizes are 14 gauge.
The bend radius (1:1) is measured at the centerline of the tubing. Multiply the tubing OD by 3 to find the donut OD. The donut ID equals the tubing OD.
* Note: The inner seam (along the inside edge of the bend) is not welded at the factory. This may cause binding when cutting the tube. A few tack welds on the inner seam prior to cutting will help to avoid binding of the saw blade. After cutting, finish by welding the entire seam.