Galvanized Rigid Metal Conduit comes in 10' lengths with nominal trade diameters ranging from 1/2" to 6". Unlike EMT which is a straight tube, rigid comes with a 3/4" NPT thread on both ends. A coupling is threaded on one end and a color-coded thread protector on the other. RED represents 3/4" and 1-1/4". BLUE is used on all even sizes (1", 2", etc) and BLACK is on all the 1/2 sizes (1/2", 2-1/2", etc). GAL can be in wet or dry locations and exposed or concealed in a variety of circumstances. As a protection against metal-to-metal contact and for oxidation related corrosion resistance, the conduit is coated with zinc using the hot-dip galvanizing process. See the product called COLD GAL to see how it applies to this conduit.