In this paper the author discusses the fact that economists define optimal IP rights as a continuum of options in three dimensions: height, breadth and length. At the operational level he discusses the impossibility of multiplying rights indefinitely (due to prohibitive transaction costs), as well as the use of a limited number of IP tools which have led to the implementation of flexibilities. These flexibilities are designed to limit certain perverse effects of rights ill-adjusted to the characteristics of some economic sectors (agricultural biotechnologies, pharmacy, etc.). In this context, the author analyses how these flexibilities are implemented in TRIPS and TRIPS agreements and he studies the consequences for Developing Countries.