Invisalign aligners are made out of SmartTrack material, a plastic material often made from polymethyl methacrylate (PMMA) which is a clear, durable and flexible material. Invisalign is known to be a lot more lightweight and comfortable than traditional braces. The smooth plastic of the aligners eliminates the possibility of your skin, tongue, lips, etc. from getting caught in the metal brackets traditional braces are made from.