It mounts under dash. Measures 5 inch width x 3-3/4 inch height x 2 inch depth outside dimension and 3-1/8 inch width x 2-1/2 inch height x 1-1/2 inch depth cutout dimensions. 21 Volt 10 Amp at 12 Volt using 18 gauge wire or 20 Amp at 12 Volt using 14 gauge wire rated.