The Plate Mate protects your guitar's bridge plate from damage caused by ball-end strings and enhances your tone too! Brass plate installs in minutes with no tools required, held in place by the strings' ball-ends or with supplied two-sided tape. The Plate Mate can also be used to protect from further damage bridge plates that are already eroded, but not yet cracked. 2 3/8" spacing. This one was made to fit a 30's Kalamazoo flattop, may fit others.