combination of polyester component a and resinous component b will comprise from about 20 to about 99 parts by weight and the filler will comprise from about 1 to about 80 by weight of the total composition i e the combined weights of components a and b and the reinforcement in particular the preferred reinforcing fillers are of glass and it is preferred to use fibrous glass filaments comprised of lime aluminum borosilicate glass that is relatively soda free this is known as 34 e 34 glass however other glasses are useful where electrical properties are not so important e g the low soda glass known as 34 c 34 glass the filaments are made by standard processes e g by steam or air blowing flame blowing and mechanical pulling the preferred filaments for plastics reinforcement are made by mechanical pulling the filament diameters range from about 0 00012 to 0 00075 inch but this is not critical to the present invention the length of the glass fliaments and whether or not they are bundled into fibers and the fibers bundled in turn to yarns ropes or rovings or woven into mats and the like are also not critical to the invention however in preparing the present compositions it is convenient to use the filamentous glass in the form of chopped strands of from about 1 8 to about 1 inch long preferably less than 1 4 inch long in articles molded from the compositions on the other hand even shorter lengths will be encountered because during compounding considerable fragmentation will occur this is desirable however because the best properties are exhibited by.