General 7200 Fiberglass Folding Rule. The General 7200 Fiberglass Folding Rule extends up to 6" (72"), with 7" breaks that can be locked at 90 and 180 degree angles. In addition, there is a thin, 6" extension for taking measurements in tighter spaces. The Folding Rule is constructed of high-impact plastic with fiberglass reinforcement for added strength.