Precise determination of $\alpha_s$ from the $C$-parameter distribution
nal states coming from the underlying partons created in the collisions appear as boosted and collimated groups of hadrons known as jets. Event shapes have proven to be very successful to study these collisions quantitatively. They combine the energy and momenta of all of the measured hadrons into an infraredand collinear-safe parameter which describes the geometric properties of the whole event by a single variable distribution. Due to their global nature event shapes have nice theoretical properties, making it possible to obtain very accurate theoretical predictions using QCD. Most e + e event shape variables quantify how well the event resembles the situation of two narrow back-to-back jets, called dijets, by vanishing in this limit. Because the dijet limit involves restrictions that only allow collinear and soft degrees of freedom for the nal-state radiation, such