You can buy it from Archie, a mechanical engineer in Prondra. The price is 3000000 Zeni. After opening, it can be exchanged for 16 kinds of magic helmets, which are only used by mechanics. Rong Yinghui's light armor and its matching light helmet used by the royal machinist of Luen Kingdom are the symbol of the highest scientific and technological productivity in the Kingdom, and it is not allowed to dye clothes. It is said that the cost of building one is equivalent to rebuilding a castle.