spare parts) are combined into a single offering. Examples The following existing offerings illustrate the PSS concept: Xerox' pay-per-copy model for selling office equipment Rolls-Royce's Power-by-the-Hour service package for aircraft engines, whereby maintenance, repair and overhaul services are charged per hour of flight Atlas Copco's Contract Air service, whereby air compressors are sold per m3 of compressed air delivered Philips' pay-per-lux model for selling lighting equipment, whereby customers pay for a promised level of illuminance in a building Michelin's fleet management solution whereby truck sold per kilometer driven Case study In the framework of the European research program of TURAS (Transitioning towards urban resilience and sustainability), a study, in Belgium, explored new hybrid-combinations between products and services systems in order to develop new creative and sustainable business opportunities (both economically viable and creating new jobs) for the Brussels-Capital Region. Five workshops have been organized on the following topics: After 5 co-creation workshops, with more than 50 different stakeholders, and the use of specifics tools, 17 PSS inspiring and promising ideas were identified. After a selection process 4 were chosen for further development of their business models through a series of tools (debugging, light experimentation, simulation, etc.). The study led to the development of a practical toolkit (freely downloadable): PSS Toolkit – Development of innovative business models for product-service systems in an urban context of sustainable transition. Impact Several authors assert that product service systems will improve eco-efficiency by what is termed "factor 4", i.e. an improvement by a factor of 4 times or more, by enabling new and radical ways of transforming what they call the "product-service mix" that satisfy consumer demands while also improving the effects upon the environment. van Halen et al. state that the knowledge of PSS enables both governments to formulate policy with respect to sustainable production and consumption patterns, and companies to discover directions for business growth, innovation, diversification, and renewal. Tietze and Hansen discuss the impact of PSS on firms' innovation behavior identifying three determinants. First, product ownership is not transferred to the customers, but remains with the PSS operating firm. Second, the purpose of a product is different if it is used within PSS solutions than compared to the purpose of products in classical transaction based business models. When offering PSS, products are used as a means for offering a service. Third, the profit function of PSS operating firms differs substantially from profit