Proflow's Donut Tubing is available in stainless or mild steel, and in a wide range of sizes to fit almost any project. Formed to the 1D sizing standard, our donuts allow for very tight radius turns with a smooth, wrinkle free uniform surface to optimize airflow. Donuts are perfectly formed, so your finished products flow properly, regardless of orientation. Simply cut the shape you want out of the donut, position and weld. Donuts may also be used with standard U-Bends to efficiently fabricate challenging projects. Donut Tubing is so well-finished. Whether you are moving air through an engine or creating a metal sculpture, you've come to the right place.