These MTI-3 series Chromalox Incoloy Screw Plug Immersion heaters for solution waters have a 2 ½ inch NPT(M) stainless Steel Screw Plug and Incoloy sheathed electric heating elements. The Watt Density is between 46 and 51 and total wattages from 3 to 18 kw (kilowatts). Voltages come in 240 and 480 3 phase with General Purpose (NEMA 1), Moisture Resistant (Nema 4 – E4TP style) and explosion resistant (NEMA 7 – E2 style) enclosures. The E2 enclosures are CSA and NRTL/C certified. The General Purpose enclosures are UL and CSA approved. Any heaters exceeding 48 amps are NOT UL, CSA or NRTL/C certified (approved).