Sure Thik Hair Strengthening Serum, 4.4 Ounce by Sure Thik. $37.55. Stops hair loss and promotes hair growth. Safe, non irritating, and proven to strengthen and re-vitalize weak and thinning hair for both men and women. Thickens and strenghtens hair growth. Sure Thik hair serum is a topical, natural based treatment for daily use. It reduces the dht levels to increase circulation to the scalp and provide vital nutrients directly to the hair follicles.