Rate of Tax for Wirks Contact

My client is registered under GST act in Mysore and executing Fabrication works Contract to KRIDL on various parts of Karnataka. But we are having a doubt that few people says that it is 12% Rate of Tax and few people says it is 18%. Even in KRIDL we could not get the correct reply. But some of them are telling KRIDL is a Govt of Karnataka undertaking was started as a Directorate of Land Army in the year 1971 and it was Incorporated as a company in 1974 under and complete ownership of govt of Karnataka. Please can anybody explain me the GST rate of Tax to raise Invoice to KRIDL.