The use of RTM (Resin Transfer Moulding) for Aerospace Components is starting to be a reality. RTM gives the possibility to produce from small to very large parts in a single process. In this paper we are going to explain how a 2x1x0,125 m(3) Fin-Box was manufactured. The requirements, the simulations, the mould design, the materials used, the scale model tests, the first trials, and finally the very sound part achieved are described below.