BAYBOND PU 402 A is an anionic/non-ionic polyester urethane polymer dispersion used as a film-forming component in glass fiber sizes. BAYBOND PU 402 A provides outstanding film-forming properties and very good adhesion for glass fiber sizes. It has high colorfastness, even at elevated temperatures and is very stable against shear forces. BAYBOND PU 402 A can be thinned in any ratio with deionized water and is compatible with commonly used additives. Glass fiber sizes based on BAYBOND PU 402 A are characterized by their ability to reinforce materials while maintaining durability and longevity even under stresses.