Two different sizes made from 3-ply B-W-B plastic. The larger cover, 2.25" or 56.9mm diameter, fits most pre-serial # (1974 and earlier) guitars that typically have six screw control cavity control cavity covers (Ibanez). The smaller cover, 2.15 or 54.7mm diameter, fits most post 1974 guitars that have 4 screw control cavity covers as well as later Artists and Professional series. Please check the dimensions to make sure you are ordering the correct cover.