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. 2 1/8" spacing is used in most guitars from 1939 to the present. The Plate Mate can also be used to protect from further damage bridge plates that are already eroded, but not yet cracked. This one was made to fit a 30's Kalamazoo flattop, may fit others.