Material: 0.75" MDF (3/4" inch) Includes: 1 Pair (2 rings total)Made in-house, In the USAGP's in-house made CNC 4" Speaker Rings.Inner Diameter: 3.7"Outer Diameter: 4.7"For 4" Speakers with a mounting diameter of 3.70" or smaller. Fits all common 4" speakers with a cutout of 3 5/8 and 3 11/16 or less