The effect of mixhead geometry on the impingement mixing in the reaction injection molding (RIM) process is largely unknown. In this study, high speed photographs are used to show the flow patterns produced by L shape mixheads. The mixing quality of the conventional I and various L shape mixheads is quantified by an emulsion test. The adiabatic temperature rise of a polyurethane/urea system is followed to further characterize the mixing produced by I and L shape mixheads. The results show that L shape mixheads give a better mixing quality than the I shape mixhead, especially at lower Reynolds numbers. In addition, the L shape mixheads can provide a more laminar flow from the mixhead, which is important for mold filling.