Intended for general purpose applications, THHN building wire is 19-strand, 600-V uncoated copper wire available in gauge sizes ranging from 4 to14. It’s suitable for use in wet or dry locations. MTW-type wire is available in 19- and 26-strand, 600-V bare, annealed copper in 10- to 16-gauge sizes. Its primarily uses include control cabinets, machine tool applications, and appliance wiring applications. Both wire types are UL-, cUL-, CSA-, and NEMA-rated.