Aluminum alloy; 5.250in. Lg; 4.562 in w; 0.500 in. H; bracket consists offront and back plates; front plate with 5 mounting holes 0.375 in. Diameter and 4 mounting holes 0.125 in. Dia; back plate with 5 mounting holes 0.188 in. Diameter and 4 mounting holes 0.125 in. Dia