A drive chain for a needle of a circular knitting machine, wherein the drive chain, once mounted to the circular knitting machine, is inserted into a respective longitudinal groove of a needle-holding cylinder of said machine, is located below a respective needle and is operatively placed between the respective needle and actuating cams of said machine, said drive chain comprising: - a sub-needle arranged below the needle and engaged to the needle so as to move axially in the respective longitudinal groove together with said needle; wherein the sub-needle comprises a butt radially movable between an operating position, in which it is extracted from the needle-holding cylinder so as to engage with respective first paths defined by first actuating cams and cause the needle to be activated, and a non-operating position, in which it is retracted in the needle-holding cylinder so as not to engage with said first paths; - a selector partly located below the sub-needle and partly beside the sub-needle, wherein the selector is configured for oscillating between an active position, in which it pushes the butt to the operating position, and a rest position, in which it allows the butt to get back to the non-operating position, wherein the selector is axially decoupled from the sub-needle and from the needle so that the needle and the sub-needle are never pushed or pulled along the axis of the longitudinal groove by said selector; the drive chain being characterized in that the selector is a flat part comprising a main flat body and a pair of springs protruding on opposed sides of the main flat body and resting against opposed surfaces of the respective groove; wherein, when the selector is inserted into the groove, each spring pushes against the respective surface of the groove, so as to optimize oscillation of the selector in said groove and to stabilize the selector in said groove. said drive chain comprising: - a sub-needle arranged below the needle and engaged to the needle so as to move axially in the respective longitudinal groove together with said needle; wherein the sub-needle comprises a butt radially movable between an operating position, in which it is extracted from the needle-holding cylinder so as to engage with respective first paths defined by first actuating cams and cause the needle to be activated, and a non-operating position, in which it is retracted in the needle-holding cylinder so as not to engage with said first paths; - a selector partly located below the sub-needle and partly beside the sub-needle, wherein the selector is configured for oscillating between an active position, in which it pushes the butt to the operating position, and a rest position, in which it allows the butt to get back to the non-operating position, wherein the selector is axially decoupled from the sub-needle and from the needle so that the needle and the sub-needle are never pushed or pulled along the axis of the longitudinal groove by said selector; - a sub-needle arranged below the needle and engaged to the needle so as to move axially in the respective longitudinal groove together with said needle; wherein the sub-needle comprises a butt radially movable between an operating position, in which it is extracted from the needle-holding cylinder so as to engage with respective first paths defined by first actuating cams and cause the needle to be activated, and a non-operating position, in which it is retracted in the needle-holding cylinder so as not to engage with said first paths; - a selector partly located below the sub-needle and partly beside the sub-needle, wherein the selector is configured for oscillating between an active position, in which it pushes the butt to the operating position, and a rest position, in which it allows the butt to get back to the non-operating position, wherein the selector is axially decoupled from the sub-needle and from the needle so that the needle and the sub-needle are never pushed or pulled along the axis of the longitudinal groove by said selector; the drive chain being characterized in that the selector is a flat part comprising a main flat body and a pair of springs protruding on opposed sides of the main flat body and resting against opposed surfaces of the respective groove; wherein, when the selector is inserted into the groove, each spring pushes against the respective surface of the groove, so as to optimize oscillation of the selector in said groove and to stabilize the selector in said groove.