Daisy Kalnina, founder of The GelBottle Inc., says Hard BIAB boasts the same easy application and self-leveling formula (for a professional-looking, smooth, and even finish), but is designed to be much more rigid and durable. “It’s a hybrid gel that combines the strength of a traditional hard gel with the simplicity of BIAB,” adds Kalnina, “so if you want serious length, whether that’s growing out your natural nails or doing sculpted extensions, this is what you need.”