RAM; Tough-Mag; 66MM Diameter Ball Base Looking to mount to a metal surface? The RAM; Tough-Mag; 66mm diameter base is the powerful and durable solution you’ve been searching for. With a B size ball screwed into a ¼-20” threaded post, simply attach a compatible double socket arm and your desired RAM; device holder. This base features an industrial-strength N35 grade magnet and rubber coating that protects the metal surface you’re attaching the RAM; Tough-Mag; to. | RAM Mount ; Tough-Mag; 66MM Diameter Ball Base