Utilizing the benefits of modular products is an industrial phenomenon that has emerged in second quarter of 20th century. This was made possible by developments in manufacturing technologies such as standardized quality of materials, tolerance levels and methods that enabled benefits through repetition. There are many examples in history where modular products have turned out as success stories. Equally, there are many examples of modular product that have never proceeded beyond prototype stage and have ended up as commercial failures. In this paper we discuss the factors that affect to exploitation and success of modularity. In previous research several factors, based on business and technological issues alike, have been presented. However, these factors do not really explain the success or failure of cases presented in this paper which represent equipment in capital goods sector; locomotives with electric traction, bus manufacturing and shipbuilding. These cases are explored with two questions in mind: is the size or weight of the products limiting modular approach and are the factors effecting modularity due to internal product characteristics or external properties such as business environment? In our conclusion we present that the ruling factor affecting modularity is the existing business environment. However, increased size of products typically has effect to manufacturing technologies due to challenges in tolerances and required investment to manufacturing facilities thus requiring manual work which hinders repetition in manufacturing and modularity benefits.