... recognition. Rigid metal conduit is available in trade sizes 1/2 through 6. Thread protectors for trade sizes 1, 2, 3, 4, ... 5, and 6 are color-coded blue, trade sizes 1/2, ... 2-1/2, 3-1/2 are black, and trade sizes 3/4 and 1-1/4 are red. The ... feet. Twenty foot lengths are available in some trade sizes.For more products catalog please contact our company.