Major (original brand DRAM ICs) are manufactured by DRAM makers, using the best quality wafers and following the original factory’s comprehensive testing procedures. These ICs are printed with the manufacturer's trademarks, such as Samsung, Micron, or SK Hynix. Users can clearly identify the specifications and manufacturers of the IC and enjoy the advantages of the manufacturer’s warranty. The eTT (effectively-tested DRAM) DRAM ICs have been tested for effectiveness but have not been fully tested. They are of lower quality than the major-grade DRAM IC. Downstream DRAM module makers are the primary buyers and attach their own trademarks to the ICs. The uTT (untested DRAM) DRAM ICs are not tested after packaging. The quality is usually less assured. They are also purchased by downstream DRAM module manufacturers and printed with various trademarks. Finally, the Downgrade DRAM are made from wafers and dies with poor yields and mixed with ICs that have not been screened or tested. This may even include ICs that have failed tests at higher certification levels. This level of IC often has serious compatibility issues, high defect rates, and cannot meet most quality requirements.