This report introduces the REFLOW Framework as a supportive model to enable agency and participation of municipalities, SMEs, and citizens��� associations in the development of CE practices and governance. After introducing the key terminology informing the REFLOW's understanding of cities' transition towards CE, this deliverable provides the most updated version of the REFLOW Pilot Cities��� Circular Action Plans, including their final list of key performance indicators, and main implementation challenges encountered so far. Based on insights from research and practice, as well as from the experience of the first two years of the REFLOW project, the REFLOW Framework integrates key concepts from systems thinking, management accounting, iterative design, and Circular Economy research to understand and describe circular transitions in cities. As a supportive model, the REFLOW Framework enables to unpack the inherent complexity characterising cities' transitions towards Circular Economy, and inform management, governance and implementation of Cities' Circular Action Plans. The Framework described in this deliverable will serve as a baseline to support Cities' Ecosystem Design and the development of the REFLOW Legacy in the last year of the project.