Size 28 XXXX Cork Stoppers are our premium grade tapered corks. Size 28 XXXX Corks are suitable for labratory, oils and moving liquids. Made from 100% natural and sustainable cork. No minimum order required. Bulk cork stoppers for sale with volume discounts at wholesale prices. WidgetCo products are manufactured to exacting standards to provide a secure seal every time. All stoppers are visually sorted and graded by the size of the lenticels (crevices) that occur naturally in the cork. Our premium grade are popular for many labratory and food packaging application.