Abstract: Commercial Off The Shelf tools (COTS) are now widely distributed, of good quality, relatively cheap and cover most of the application domains. It is thus a surprise to consider that it is uncommon to reuse COTS when building large applications. At least it is recognized that building a large application based on COTS is a tough issue. This paper seeks to show why COTS reuse is not a reality; we show why usual composition does not work, and what are the issues to solve in order to make effective (re)use of COTS when building new applications. We show the solutions we have applied, and we describe the early experience with our prototype.