All Indian paratroopers are volunteers. Some enter the Para regiments fresh from recruitment, while others transfer in from regular army units. They are put through a probationary period / selection process of three months for Paratroopers (Airborne) Battalions (5,6,7,23,29) and six months for Para (Special Forces) battalions (1,2,3,4,9,10,11,12,21 PARA), in order to be a Para (Special Forces) all personnel are first required to qualify as Paratroopers; once selected the candidates may choose to advance to the SF selection, which takes place twice a year in the spring and the autumn term.