To provide glass compositions that are useful in electronic applications, such as reinforcements in printed circuit board substrates, having reduced dielectric constants relative to E-glass, while having fiber forming properties that are more industrially practical than D-glass.

A glass composition comprises 60-68 wt.% S1O₂, 0-2 wt.% Li₂O, 7-13 wt.% B₂O₃, 0-1 wt.% Na₂O, 9-15 wt.% Al₂O₃, 0-1 wt.% K₂O, 8-15 wt.% MgO, 0-1 wt.% Fe₂O₃, 0-4 wt.% CaO, 0-1 wt.% F2, 0-2 wt.% TiO₂, and 0-5 wt.% of other constituents.