BackStopp™ Acoustic InsertAbsorb distortion producing reflected waves and reduce sound transmitted through walls. Absorbs harmful reflected waves that cause speaker distortion. Helps balance mid range response and "tighten" sound cavity acoustics. Reduces sound transmitted through back wall into others rooms. Adds 'R value insulation to BackBoxx installations. Effective on all open back drivers. Dimensions: 22. 5" x 14. 5" x 1" Quantity: 1,6