Universal 10" Speaker rings. Made from Polyurethane, Paintable, Bonds and fiberglasses well. Great for drop rail bags or adding Subwoofers and Midbass speakers to a custom location tour packs, trikes.etc. They are a little over 11" OD with a mounting diameter of 9.4 for all those Bigger subwoofers and midbass speakers, Most of those sizes can be found on the manufactures website. it maybe necessary to open up the mounting diameter if larger than 9.4.