"I usually run in the opposite direction of any hair oil for fear of completely weighing mine down, but after getting a bob haircut last month — and therefore either straightening or curling it every day thereafter — I've noticed moisture has actually been running away from me. Here to help is the lightweight R+Co Two Way Mirror Smoothing Oil ($32): it's formulated with heavy hitters like moringa and argan oils to inject a dose of hydration into my ends without ever feeling greasy. The best part? You only need one pump, which means this bottle will last me . . . oh, I don't know, two lifetimes." — Kelsey Castañon, senior editor, Beauty