The stroke follows the shoulders, so aligning them is critical.

The Shoulder for the EyeLine Putting Alignment Mirror gives an expanded view of the shoulder alignment.  Match your shoulders to the mirror lines and you are ready for more solid, end-over-end rolls.  No more cut putts.

Just slide the shoulder mirror against the bottom edge of the putting mirror.  No attachment.

Turn the shoulder mirror around for a great arc template, too.