Technologies like the Internet of Things (IoT) are offering new opportunities and posing serious challenges to firms, forcing them to create entirely new business models, migrating from the conventional product-centric approaches to (digitally-based) service-oriented ones. This paper - following a qualitative research method - aims at describing the service-oriented impact of IoT technologies on firms business models, with a particular focus on opportunities and challenges for BtoB manufacturing firms. Being the impact of IoT technologies on businesses a quite recent research stream, to date scarce attention has been devoted to the topic with specific attention to its impact on service-oriented business models in manufacturing firms. The paper contributes in this research stream in different ways. It proposes a map of digital servitization that helps in understanding firms strategic transitions caused by technologies, making both theoretical and managerial contributions. Firstly, the research underlines the impact of the firms sales model as a strategic factor in shaping firms digital servitization strategies. In addition, three progressive levels of digital servitization complexity are identified, namely product- process- and outcome-oriented, that are based on an increasing use of IOT technologies and have specific challenges and opportunities.