Cogwheel

Cogwheels are items that fit exclusively in Cogwheel sockets, much in the manner of cut gems. Currently the only items having Cogwheel sockets are Bio-Optic Killshades, engineering crafted head items. It requires an engineering skill of 525 or higher to enable these gems.

Source
Cogwheels are sold by the following vendors:


 * in Stormwind City
 * in Ironforge
 * in Highbank, Twilight Highlands
 * in Orgrimmar
 * in Orgrimmar
 * in Dragonmaw Port, Twilight Highlands

The Twilight Highlands vendors can only be accessed after completing a short chain of quests, which require level 84 or higher.

Description
Currently, all Cogwheels are unique-equipped, preventing a person from doubling up on any of them.