Authentic Tiffany & Co. 18K Yellow Gold Butterfly Earring Back Backing Tiffany & Co. 18K yellow gold single butterfly style earring back. If you have ever lost a backing to one of your beautiful gold Tiffany & Co. earrings, here is your chance to get another one. Single backing weighs 0.3 grams. Butterfly top measures 7mm. long, round bottom part of backing measures 5.8mm. wide. Brand new and never worn!