The model number SM-G991U points to vanilla Galaxy S21. The other two model numbers SM-G996U and SM-G998U point to Galaxy S21+ and Galaxy S21 Ultra respectively.
Recently, the Galaxy S21 and Galaxy S21+ spotted on 3C certifications. It reveals that the S21 will feature a 3,880mAh battery while the S21+ features a 4,660mAh battery. Note that these are rated battery capacity, and typical battery capacity is always higher. Hence, we expect the vanilla Galaxy S21 to have a 4,000mAh typical battery capacity.
