Nitro-tuff tubes are available in honed and nitrided and honed, nitrided and polished. Nitrided tubes are an enviromentally friendly alternative to Chrome Plated ID tubing. Nitrided tubes have a hard as chrome top layer as well as a hard diffusion zone that acts like a shallow case induction hardened surface. Our AC Models stock sizes include 1-3 / 4 x 1-1 / 2, 2-1 / 4 x 2, 3-1 / 4 x 3, 4-1 / 4 x 4, 5-1 / 4 x 5, 6-1 / 4 x 6, 8-1 / 2 x 8, 10-1 / 2 x 10, 12-1 / 2 x 12 and 14-1 / 2 x 14. All AC models are also available in our ACP line. This is a honed, nitrided and polished product.