Purpose – There is a challenge in how to achieve an efficient and competitive production environment in manufacturing companies that customize their products to a large extent. Henceforth, the study examines how a material flow can become more efficient without disrupting the current customization demands. The purpose of the study is; To investigate how to increase material flow efficiency in manufacturing companies that customize. Based on the purpose of the study, three research questions have been formulated. -        How does the current material flow look like in manufacturing companies that customize? -        What affects the efficiency of material flow in manufacturing companies that customize? -        How to increase the efficiency of material flow in manufacturing companies that customize? Method – This is a case study, with the data collected in documents, observations, and interviews. Method triangulation was used to increase the credibility of the findings. The study's data collection is also linked to the theoretical framework to create a credible result. Findings – The results of the study showed a current state of the company's material flow through the use of value stream analysis and cycle time analysis. The wastes: inventory, unnecessary transports, unnecessary relocations, and waiting were identified. The lean principles continuous flow and equalization of the workload were found to be particularly relevant. The tools WMS-system and ABC-analysis were also found to be relevant for increasing the efficiency of material flow.  Implications – Companies should use value stream analysis as a tool to identify waste in material flows. Furthermore, manufacturing companies that customize should use the lean principles, as well as the use of WMS systems and ABC analysis to make their own material flows more efficient. Limitations – The study only examined one case of manufacturing companies that customize, which undermines the external validity. One limitation is also that the data collection was carried out for a short period. As the examined material flow was not repetitive, the times for the process’s cycles varied, which reduced the quality of the study. Keywords – Lean, waste, high-mix and low-volume, efficiency, material flow