250mL Glas-Col Heating Mantle, Series TM, Spherical, 180 Watts. The Glas-Col Series TM spherical flask mantle covers only the flasks bottom half, letting you see its full contents. The Series TM mantle is available with a bottom hole for flask drain on a special order basis. Terminal box models are available with switches and pilot lights. Mantles are 115 Volt.