Cal. Veh. Code § 24610

A reflector placed on vehicles under Section 24609 which is of the button or other multiple-unit type shall contain not less than seven units with a total of not less than three square inches of reflecting surface. The red reflectors required may be separate units or a part of the red taillamps, but in either event the reflector and taillamps shall comply with all of the requirements of Sections 24600, 24602, and 24609, and any reflector constituting an integral part of a taillamp shall comply with all photometric requirements applicable to a separate reflector.