The DV-90 is a 3-part assembly made up of a lower mount joint, an upper whip joint and a wing-nut locking set.  The purpose of this accessory is give you the ability to correct the antenna mounting angle or allow you to easily fold your antenna down and out of the way.  The DV-90 has standard 3/8"-24 threads on both ends so you can place it between your antenna and mount to gain the added features it offers.  The entire assembly is 2.25" (57mm) tall and is finished in a classy black chrome.