Every product of Goodbong company has hologram register label, on which marked the date of production, if there is any problem of quality inguarantee period, Goodbong will take the responsibility. We will fabricate and change the new products for free, if the customer want to slove the problem himself, then all the cost can be taken by our company, but the total cost limit is 2 times value of the changed products. if there are any problem in using period, Goodbong can provide the new products for free, but we will not be responsible for any other charges.