Home Skin b.glen c serum: Can 7.5% Vitamin C Rival 15% Formulas? Skin b.glen c serum: Can 7.5% Vitamin C Rival 15% Formulas? By - November 6, 2024 19 0 FacebookTwitterPinterestWhatsApp Skincare brands take notes: this is how you formulate a serum that will stay effective for over a year. Source ..