Standardized footprint for easy replaceabilityThese popular mounts are the standard for marine antennas, but since they have traditionally been made by different companies, they end up with different hole patterns and appearances. We've taken the nylon version and duplicated it in Zamak for inland users, and in stainless steel for ocean users. One can easily replace another if needed. Fits all standard 1" marine antennas. Features 4-way ratchet design. Base measures 2 1/2" x 3 9/16" Mount with 1/4" FH fasteners