A sling assembly for treatment of stress urinary incontinence may comprise a midline marker, a sling, and a sleeve. The midline marker identifies the midpoint of the protective sleeve when it is installed on a transparent surface of the sleeve. The protective sleeve comprises a clear transparent surface and a colored opaque surface. During a procedure, the colored opaque surface of the sleeve provides contrast between the surfaces of the sleeve to identify any twisting present throughout the length of the sleeve. The clear transparent surface of the sleeve forms a channel at the center of the midline marker when the transparent surface of the sleeve is wrapped over the body of the midline marker. The channel is large enough for a surgical instrument to be inserted and cut the transparent surface to separate the sleeve from the midline marker after installation of the sling at a desired location.