The ceremony called vestizione (the dressing) marks the beginning of sa Sartiglia.
It is a long and complex ceremony during which the various traditional clothes are sewn together on the post around the body of the soon-to-be su Componidori. The ceremony serves the function of transforming the chosen horseman into su Componidori, which is the leader of the race and represents a genderless deity.
On the morning of the race, su Componidori visits the riders in their stables, then goes to the house of the president of the guild. From there, a procession of trumpeters and drummers, of Massaieddas and sa Massaia manna, and finally of the members of the guild and su Componidori, goes to the seat of the guild, where the ceremony will take place.
Once there, the soon-to-be su Componidori is seated on a chair put on top a table known as mesitta. From that moment on, su Componidori will not be allowed to touch ground until the end of the day.
A group of young girls called Massaieddas bring the clothes to the venue where the vestizione will take place. They dress up su Componidori under the supervision of sa Massaia Manna, an older more expert woman which closely oversees the doings of the massaieddas, giving them instructions on how to properly dress su Componidori. The women are all dressed in the traditional clothes from Oristano.
Two horsemen will be invested of the role of su Componidori, the one in charge of leading race on Sunday and the other on Tuesday. Their costumes are overall very similar, but they differ in colours and some details because they represent two different guilds.
Su Componidori of the Gremio dei Contadini (the farmers guild) wears a white shirt whose puffed sleeves are held together by red ribbons. On top of the shirt, su Componidori wears a sleeveless jacket reminiscent of the old trade working uniform, known as coietto, which is tightened on the chest with leather laces. Su Componidori of the Gremio dei Contadini wears an earth-coloured mask.
Su Componidori of the Gremio dei Falegnami (the woodworkers guild) also wears a white shirt whose puffed sleeves are held together by ribbons, but these are pink and sky-blue. Instead of leather laces, silver studs in the shape of a heart button the coietto. Su Componidori of the Gremio dei Falegnami wears a wax-like white mask.
The mask, the embroidered veil and the top hat are the last pieces to be put on su Componidori. A red camelia decorates the jacket for Sunday, a pink one for Tuesday. The ceremony is now completed. Su Componidori is ready to be escorted in procession to the old city centre.