The literature in requirements engineering recognizes the product scoping activity as an important source of risks and fails in bespoke software projects. In order to help address this activity, we designed and implemented an interactive visual instrument that allows providers and customers to jointly define the scope of bespoke software products, particularly, information systems. The instrument was formally evaluated through a qualitative study that involved three projects in Chile and three in Brazil. Real customers and providers took part in these experiences. The evaluation results were highly encouraging, showing the instrument is a serious candidate to help deal with the product scoping challenges. Customers, software providers and also software engineering researchers can also take advantage of it, by reusing and adjusting the instrument to their own reality.