The RAM-D-201-SU consists of a 2.25" dia. ball compatible STANDARD LENGTH double socket arm, mixed combination Pin-Lock™ security nut and key knob. RAM® Pin-Lock™ security solutions are designed to withstand the harshest environments where RAM® Mounts are commonly used. With an emphasis on aesthetics and function, RAM® security nuts/knobs are low profile and only add a small amount of additional bulk to your system when compared to the standard knob included. At a fraction of the cost of currently available keyed locking knobs, the additional peace of mind and tamper resistance comes at a very affordable price.