Gear is a system that is used in Injustice 2.
Gear is customizable outfits for all the playable characters in Injustice 2. Some gear is only for specific characters, such as Scarecrow having a different hook. All gear can be acquired by playing matches if they do not prematurely quit during the match.
Shaders are a part of Gear, but merely used for cosmetic purposes that change color for the Gear of characters.
Premier Skins are a part of Gear that changes the character's appearance, voice and dialogue. Only certain characters will have Premier Skins.
Some gear can gain the character abilities such as extra attacks. Abilities for Gear can be enabled or disabled for multiplayer matches.