Folded from 18 gauge aluminum for rigidity. Similar to a "BB" in size, but two-level so that controls don't get stomped. The 4-40 tapped holes for securing screws are "collared" so that they won't strip out. Expensive, but worth it for special projects. Includes four screws and four rubber feet. Commercial users: Ask me about made-to-order versions with mounting studs, battery drawer, custom drilling, etc. Mechanicals can be found in the Library.