Retention Sleeve

FIG. 1 is a front, right-side, bottom, perspective view of a retention sleeve embodying the design; FIG. 2 is a rear, right-side, top, perspective view thereof; FIG. 3 is a front view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a right-side view thereof; FIG. 6 is a left-side view thereof; FIG. 7 is a top view thereof; and, FIG. 8 is a bottom view thereof. The broken lines in the drawings depict portions of the retention sleeve that form no part of the claimed design.