When it comes to the cost-effective production of high-strength lightweight parts in large volumes, the length of the structural reinforcing fibers is of key importance. The rule of thumb here is: the longer the fibers incorporated in the plastics, the greater the resilience of the final products. The fiber length and content cannot be influenced in the case of ready-to-use fiber-filled granulate mixes. Things are different with innovative fiber direct compounding (FDC). Here, a side feeder can be used to incorporate fiber strands of variable length in the liquid plastic melt. This allows the mechanical properties of the parts to be improved. Moreover, it also offers significant cost advantages in comparison with fiber-reinforced standard granulate.