The rigid core features special top and bottom layers for stability, and is constructed from a high-density composition for extra rigidity, providing superior dent and impact resistance. Since COREtec is 100% waterproof, COREtec Pro Plus floors can be installed in wet areas and will never swell when exposed to, or even submerged in water. COREtec is also dimensionally stable, so it will not expand or contract under normal conditions, and never needs expansion strips in large rooms. Each COREtec Pro Plus plank or tile has an attached cork underlayment for a quieter, warmer vinyl floor that is naturally resistant to odor causing mold and mildew. All styles in the COREtec Pro Plus Collection feature the patented COREtec® technology.