Three-prong 18 karat white gold stud featuring 7.0-mm cubic zirconia weighing a total of 4.45 carats with a heavy 8-mm friction back. by Ely Urbanski | Sep 4, 2021 Three-prong 18 karat white gold stud featuring 7.0-mm cubic zirconia weighing a total of 4.45 carats with a heavy 8-mm friction back.