Currently many companies base their marketing strategy around a family of products. Thus, they regularly add new variations to products in order to meet changing market needs, or to attract new customers. Although the basic functionality remains unchanged across products, new features, aesthetic appearance and technologies are incorporated in each new product. This if it is not checked, can generate the “complexity of the product,” which leads to a loss of productivity or quality. Thus, the effective management of product variations in design and manufacturing is challenging. The key is minimizing the non-value added variations through models within a range of options without limiting customers. This article discusses the factors that contribute to the "complexity of the product” and this is done through the product line commonality index (PCI) , which measures the level of common parts in a product family. A case study of bicycle frame displays its implementation and functionality. The index shows the possibility that the products in a family share parts effectively (modularity) and reduces the total number of parts (multifunctionality).