This document discusses cost estimation models for identifying faulty objects when reusing object-oriented software components. It begins by introducing the benefits of reusable object-oriented components for reducing software development costs and time. However, sometimes these existing components contain "faulty objects" that are incompatible with new software systems and cause errors. The paper focuses on developing approaches to identify these faulty objects within reusable components. It reviews previous work on testing and fault detection techniques. It also discusses the need for reengineering existing components to estimate costs and identify incompatible objects. The document proposes using a reengineering cost model that considers the number of reused objects and their attributes to estimate identification efforts for faulty components. The goal is to determine if reusing or redeveloping is