Abstract: A glass composition which can be drawn into continuous filaments at a temperature of 1050.degree. C. or below, without risk of devitrification (crystallization), comprises by weight:______________________________________ % ______________________________________ SiO.sub.2 49-55 Al.sub.2 O.sub.3 2-4 B.sub.2 O.sub.3 7-10 Na.sub.2 O 14-18 K.sub.2 O 0.5-3 CaO 8-12 ZnO 1-4.5 ZrO.sub.2 1-7.5 ______________________________________and has a 1000-poise viscosity temperature not greater than 1050.degree. C. and a liquidus temperature at least 20.degree. C. below the 1000-poise viscosity temperature.