Pressure drop variability is an important quality parameter in filter rod production. It can be influenced by the quality of the filter tow used, type of plug assembling machine and certainly the filter rod making process. Even the way of sampling can strongly influence the measured values. This paper will describe a mathematical process to quantify the individual contribution to pd variations as a result of weight, circumference and pressure drop yield variations. By far the biggest impact on pressure drop variations is caused by rod weight variations. One essential cause for rod weight variations is the transport system. We tested different transport systems and have identified the potential for improvement product or process analysed and interpreted by the described mathematical tool.