Outside dimensions are 3-17/32" (89.69mm) x 1-25/32" (45.24mm), inside is 2-3/4" x 1-1/2" (69.85mm x 38.10mm). Each mounting ring has a flat (non-arched) bottom, and must be trimmed or sanded to match an arched guitar top.
#1507 and #1509 are low mounting rings for use at the neck position on instruments with a Gibson style bridge, and can be used at the neck and bridge positions with a Fender style bridge. The height tapers from 3/16" to 1/4" (4.76mm to 6.35mm).
#1508 and #1510 are tall mounting rings for use at the bridge position on instruments with a Gibson style bridge, and are too tall for Fender bridges. The height tapers from 3/8" to 7/16" (9.53mm to 11.11mm).