With the "Extended Upgrade System" you can Upgrade your Equipment and Weapons to +20 with better stats!
At level 13/16/18 and 20 you will also receive one additional diamond slot each.
For the Upgrade you need Scroll of UProtect (Ultra), which you can Exchange at [Cash Shop]Laura in Central Flarine,
and Ultra Sunstone's wich you can farm in Les Britannia, Abyssal Cove, Aminus and Cursed Aminus(Exchange at Dungeon Exchanger for chips).
Note: The Chance to Upgrade your items is lower then from +1 to +10!