Influence of the height of the molding cavity and the injection speed for three PP grades with different mass melt flow rate (MFR) on the molded parts mass and longitudinal shrinkage, before and after UV aging, was investigated. It was shown that the mass of the molded parts depends on the flow rate of the material and the volume of the molding cavity, while shrinkage depends only on the volume of the mold cavity and is greater after aging.