Most producing companies aim to reduce tied up capital, which is meant to increase inventory turnover. In this study, an EMS (Electronic manufacturing service) -company, a contract manufacturer, will be studied. The company does not own the products themselves, but is a service company that manufactures to customers. The business has a problem that existed for a long period of time, they have a low inventory turnover among their component inventory. The company therefore wants to increase its inventory turnover in order to reduce its tied-up capital. The aim is to develop knowledge about supplier and customer relationships that affect the stock turnover rate in component stocks. In order to make calculations, it is profitable for the company to order materials multiple times for increased inventory turnover or fewer times to keep down the order cost. Case study is based on qualitative data in the form of interviews and observations. A large part of this study is also based on quantitative data from the company's MRP (material requirements planning) system. The literature is based on articles that deals with key concepts such as EOQ (economic order quantity), customer and supplier relationships. The conclusion of this study suggests that the company should use EOQ to reduce overall order cost while reducing the tied-up capital.