The RAM-111U-B consists of a short double socket arm, 2.5" diameter round base, and 6.25" x 2" rectangle base. The round base includes a 1.5" C size rubber ball and contains pre-drilled holes, including the universal AMPS hole pattern. The rectangle base also includes a 1.5" C size rubber ball and contains a variety of pre-drilled holes that are compatible with several marine electronic devices, including fishfinders and chartplotters. product dimensions Overall Height: 5.225" socket to socket length 2.5" hole pattern 4-Hole AMPS: 1.181" x 1.496"3-Hole 120-Degree: 1.812" DiameterSee Drawing plate size Rectangular Plate: 6.25" x 2"Round Plate: 2.5" Diameter ball size C Size (1.5") weight capacity Standard Use: 4 lbsHeavy-Duty Use: 3 lbs materials Marine-grade aluminum packaging type Poly Bag Weight 1.08 lb Additional Information The included plate is a universal mounting bracket with a selection of mounting hole locations. In certain applications additional holes may need to be drilled for proper fit with your electronic device.