EMT electrical metallic tubing , also commonly called thin-wall, is a listed steel raceway of circular cross section which is unthreaded, and nominally 10 feet long. twenty foot lengths are also available. covered by article 358 of the nec
emt is available in trade size 1/2" through 2" the outside is galvanized for vorrosion protection and the inside has an approved corrosion resistant organic coating. emt is installed by use of set-screw or compression-type couplings and connectors. it is permitted to have an integral coupling which is compprised of an expaned, "belled" shape of tube on one end with set screws.