Free shipping and returns on Sienna Naturals Lock & Seal Anti-Breakage Serum at Nordstrom.com. What it is: An antibreakage serum blend engineered to seal down damaged hair cuticles.Who it's for: Ideal for those with tight (3A, 3B, 3C) and coily (4A, 4B, 4C) hair, for those with twist-outs and for wash-and-go styles.Wha…