Component based software development approach makes use of already existing software components to build new applications. Software components may be available in-house or acquired from the global market. One of the most critical activities in this reuse based process is the selection of appropriate components. Component evaluation is the core of the component selection process. Component quality models have been proposed to decide upon a criterion against which candidate components can be evaluated and then compared. But none is complete enough to carry out the evaluation. It is advocated that component users need not bother about the internal details of the components. But we believe that complexity of the internal structure of the component can help estimating the effort related to evolution of the component. In our ongoing research, we are focusing on quality of internal design of a software component and its relationship to the external quality attributes of the component.