Abstract: Devices, systems and method that allow for delivery of therapeutic radiation beams of differing sizes or shapes during a radiation treatment are provided herein. Such devices can include a rotatable collimator body having multiple collimator channels of differing size or shape defined therein, the channels extending through the collimator body substantially perpendicular to the axis of rotation. The collimator body can include markers thereon to facilitate detection of an alignment position by a sensor of a control system to allow the collimator body to be rapidly and accurately moved between alignment positions to facilitate delivery of differing therapy beams during a treatment.