Design abstractions such as components, modules, subsystems or packages are often not made explicit in the implementation of legacy systems. Indeed, often the abstractions that are made explicit turn out to be inappropriate for future evolution agendas. This can make the maintenance, evolution and refactoring of these systems difficult. In this publication, we carry out a fine-grained evaluation of Reflexion Modelling as a technique for encapsulating user-targeted components. This process is a prelude to component recovery, reuse and refactoring. The evaluation takes the form of two in vivo case studies, where two professional software developers encapsulate components in a large, commercial software system. The studies demonstrate the validity of this approach and offer several best-use guidelines. Specifically, they argue that users benefit from having a strong mental model of the system in advance of Reflexion Modelling, even if that model is flawed, and that users should expend effort exploring the expected relationships present in Reflexion Models. Copyright (C) 2008 John Wiley & Sons, Ltd.