I have not been that impressed with the return-to-zero capabilities of the KTR's dustcover sight. It is rock-solid when attached, but it does not re-zero properly if you take the dustcover off and reattach. Plus, the dustcover and gas tube are held in place by brute force, and are a serious PITA to reattach, but that is a KTR-specific issue.
YMMV. Others have said that theirs returns to zero fine.
Mike