The Middle Mesolithic of the RMS area (Rhine – Meuse – Scheldt) is characterized by the sudden emergence around ca. 9,350 cal BP of completely new microlith types. The typical microliths of the Early Mesolithic that are made by steep retouch are replaced with small backed bladelets and invasively retouched points, which have been made by pressure retouch (Crombé, 2019). Until recently, it was assumed that this innovation in retouching technique was not accompanied by other technological changes. Indeed, Middle Mesolithic bladelet productions are generally described as ‘Coincy style debitage’ (Rozoy, 1968) and are considered to have been a continuation of Early Mesolithic flintknapping traditions (e.g. Gob, 1985; Ducrocq, 2001; Fagnart et al., 2008). The aim of this research project is to verify this assumption by carrying out Lithic technological research on available Middle Mesolithic assemblages from Belgium and directly adjacent countries along the Southern North Sea basin.