North Mountain Supply #5.5 Drilled Rubber Stopper - Set of 6. Drilled to fit all standard size fermenting airlocks and provides an air-tight seal to smaller mouth Jugs - necessary for proper fermentation. BPA free and made out of Food Grade materials. Maximum Temperature: 70°C (158°F). Dimensions: 1 1/8" x 15/16" To promote a positive and satisfying customer experience, this product is covered by North Mountain Supply's 30 day hassle-free replacement program, in the event the product is damaged or defective.