This document is a user manual and warranty certificate for the CTK551-CK-1 Ck electronic keyboard. The product has passed strict quality management and inspection. In case of malfunction during normal use, the user can enjoy free repairs within the specified range. The warranty period is one year. The warranty includes free repairs under normal use conditions. When requesting warranty service, the product, warranty certificate, and the store where the product was purchased or the designated repair station of Casio Electronics (Zhuhai) Co., Ltd. should be presented. The warranty does not cover malfunctions or damages caused by improper handling, misuse, fire, earthquake, water damage, lightning, rodent infestation, non-authorized repairs, modification, abnormal voltage, or battery depletion. The warranty is only valid within the territory of the People's Republic of China.