TB Series Frames The TB Series Frame is thermally broken steel frame for use where extreme temperature differences occur. It is manufactured with a P.V.C. spline which eliminates through metal contact, substantially decreasing the thermal conductivity experienced in a normal steel frame. Manufactured from 16 ga. and 14 ga. paintable galvanneal steel Available up to 6 3/4" jamb depths Exceeds the standards for insulated steel frames C.G.S.B. 82-GP-5M Comes with Fleming's high frequency hinge reinforcing Hinge reinforcing dimpled for conversion from standard weight to heavy weight reinforcing.