Mack CL front and rear side marker bulbs utilize a 1891 bulb size for replacement applications. The replacement chart covers vehicle production spanning 1991 to 1997.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mack CL uses the 1891 bulb for both its front and rear side marker positions across the 1991-1997 model years.
The 1891 is classified as a T5 miniature wedge bulb, a designation that refers to its tubular glass envelope measuring 5/8 of an inch in width.
The wedge base design means the 1891 bulb is held in place by the socket gripping the base of the glass directly, with no separate metal base or pins involved.
The 1891 operates at 12 volts and draws 2 watts, placing it among the lower-wattage bulbs used in commercial vehicle marker lighting.
The 1891 conforms to ANSI standards recognized in both the United States and Canada, indicating it meets a shared North American specification for miniature bulbs.
Because the same bulb size applies to both the front and rear side marker positions, a single bulb type services all side marker sockets on the vehicle.
The T5 form factor is a compact bulb type, commonly associated with indicator and marker lamp applications rather than high-output lighting functions.
The consistent use of the 1891 across all listed model years means no year-specific variation exists in side marker bulb fitment for the Mack CL within the 1991-1997 range.