This subdomain includes the characteristics of individuals involved with implementing, delivering, and/or receiving the innovation. It includes characteristics related to professional skills and capabilities, autonomy, and level of involvement (Dy et al. 2015; Ashok et al. 2018; Moretto et al. 2019). Some users combine use of CFIR with the Theoretical Domains Framework (TDF) (S. A. Birken et al. 2017), which was developed with the intent “…to simplify and integrate a plethora of behavior change theories and make theory more accessible to, and usable by, other disciplines” (Cane et al. 2012). The TDF contains 84 behavior change-related constructs, organized into 14 domains. TDF domains are, in turn, mapped to an even more highly synthesized representation called the COM-B system (Michie et al. 2014; 2011). The COM-B was developed as a simplified system by which to acknowledge key domains related to behavior change based on consensus of behavioral theorists and a principle of criminal law defining specific prerequisites for volitional behavior. Three of the updated Characteristics are based on this COM-B system. The COM-B posits that the broad categories of Capability (e.g., skills), Opportunity (e.g., autonomy), and Motivation (e.g., commitment) shape behavior (Michie et al. 2011). CFIR users are encouraged to draw on this extensive work and the work of other individual-level behavior change scientists (e.g., Theory of Planned Behavior (Ajzen 2011) or the Social Ecological Theory (Stokols 1996)) when more detailed theories are needed. Alternatively, users may rely on role-specific theories, for example, facilitation (Albers et al. 2020; Metz et al. 2020) and project management (Barron and Barron, n.d.; Müller and Turner 2010) theories relevant for Implementation Facilitators and Implementation Leads; leadership (Albers et al. 2020; Metz et al. 2020) theories relevant for High- and Mid-level Leaders.