A new tolerancing approach, called inertial tolerancing, is presented by the Symme Laboratory. This method consists in tolerancing the mean square deviation in relation to the target in function of the standard deviation, contrary to the traditional tolerancing which presents the tolerancing in the form of a bi-limit. Until now, scientific literature about inertial tolerancing presents several examples of which the uni-dimensional tolerancing is applied and introduces three definitions about the 3D inertial tolerancing according to Geometrical Product Specification Standard (GPS Standard). This paper introduces a tolerance synthesis based on small displacement torsors, presents the risk of use the 3D statistical tolerancing and introduces the three definitions about the 3D inertial tolerancing according to GPS Standard. This paper closes out by an opening about the conformity of a batch defined with the 3D inertial definitions.