Amazon.com: Skin Perfection Copper Peptide Serum GHK CU 1% for Face & Hair Copper Peptides for Skin, Hair, & Scalp 1% Blue Liquid for Face, Neck, Body, Scalp Multi Use Serum Booster with Sumanurica GHK CU Repairing Serum VS Numbuzin No. 6 Deep Sleep Mask How to use GHK Cu Repairing Serum SumaNurica One of the questions we often receive about our products is: Why is the GHK Cu Repairing Serum stored in two part packaging? , GHK Cu is an unstable ingredient that can slowly lose its effectiveness