Combination Coupons can upgrade your armor by placing three identical pieces of armor (including +) into the combination menu found in the shop or My Info section and consuming a coupon to upgrade them to the next level. An example of this would be combining three Spiker +2 bodies to create a Spiker +3 body. They're also used in crafting by doing the above process with three identical fragments. Combination Coupons can be found in endgame Sector maps, earned through quests or bought from the shop.