According to the national standard of jewelry and jade in China, NGTC only recognizes the selection of natural colorless oil (NGTC only recognizes cedar oil at present, and if epoxy resin is used, it is considered as filling), and the filling amount should not be too much, otherwise it will be marked as "partial filling". According to the amount of oil injected, the national inspection commission will mark in the remarks:

"improve clarity",

"slightly improved clarity",

"The clarity is moderately improved"

And "significant improvement in clarity".

International certificates, such as GIA from USA, SSEF from Switzerland, GRS from Gubyrin, CDTE from Colombia, etc. , the fill level will be displayed.