Glass fibers with low dielectric constant

Glass fibers having a low dielectric constant are composed of a glass having a dielectric constant of not more than 5 and comprise SiO2 45-65% by weight Al2O3 9-20% by weight B2O3 13-30% by weight CaO + MgO + ZnO 4-10% by weight Li2O + Na2O + K2O 0-5% by weight based on the total weight of the glass, the total proportion of SiO2, Al2O3, B2O3, CaO, MgO, ZnO, Li2O, Na2O and K2O being at least 95% by weight.