Silicone stopper expands outward within bottles to seal in freshness Seal automatically contracts when top is pulled up Stopper's precise fit won't slip or Leak, even when storing bottles lying down Stopper's precise fit won't slip or Leak, even when storing bottles lying down Stainless steel accent for an elegant touch The OXO Better Guarantee: If you experience an issue with your OXO product, get in touch with us for a repair or replacement. We’re grateful for the opportunity to learn from your experience, and we’ll make it better.