The Item Set item ability is an abstract ability base class for common Item Set operations. These operations include equip and unequip operations such as switching to the next item or toggling the equip state of an item.
Item Set Category ID
The category that the ability should respond to. By specifying a category ID it allows multiple Item Set abilities to be added each affecting only a single Item Set category. This for example allows you to switch primary weapons with one button mapping and then switch grenade types with another button mapping.