... or the integral type. Threads on the uncoupled end are covered by industry color-coded thread protectors which protect the threads, keep ... /2 through 6. Thread protectors for trade sizes 1, 2, 3, 4, 5, and 6 are color-coded blue, trade sizes ... , 1-1/2, 2-1/2, 3-1/2 are black, and trade sizes 3/4 and 1-1/4 are red ...