The HaloTag® Control Vector provides protein expression of the HaloTag® protein in mammalian cells, E. coli or in vitro expression systems dependent on human cytomegalovirus (CMV) intermediate early enhancer, T7 or SP6 RNA polymerase promoters. It can be used as a control for any HaloTag® experimental system and can be used for both stable and transient HaloTag® expression in mammalian cells; for stable expression, co-transfection with a vector containing a selectable marker is required.