Description: Made of food-safe grade silicone, environmental-friendly and non-toxic Able to be sterilized at very high temperature over 100 Degrees Celsius due to its silicone material feature Perfect acid, alkari and corrosion resistant, better than any other rubber or plastic stoppers Ideal for laboratory, household, and industrial use, various demensions to prevent oxygen from wreaking havoc with your fermenting process Smooth and tapered sides designed for exceptional sealing and optimal fit with a wide range of openings, easy to plug in or pull out, creating an airtight seal Specification: 2.5-3.4cm Hole: Height: 2.5cm/ 0.98inch; Top diameter: 3.4cm/ 1.34inch; Bottom diameter: 2.5cm/ 0.98inch 3.5-4.5cm Hole: Height: 3.8cm/ 1.5inch; Top diameter: 4.5cm/ 1.77inch; Bottom diameter: 3.5cm/ 1.38inch 3.2-4.2cm Hole: Height: 3cm/ 1.18inch; Top diameter: 4.2cm/ 1.65inch; Bottom diameter: 3.2cm/ 1.25inch 3.2-4.2cm: Height: 3cm/ 1.18inch; Top diameter: 4.2cm/ 1.65inch; Bottom diameter: 3.2cm/ 1.25inch 4-10cm: Height: 3.6cm/ 1.42inch; Top diameter: 10cm/ 3.94inch; Bottom diameter: 4cm/ 1.57inch 3-3.7cm: Height: 3cm/ 1.18inch; Top diameter: 3.7cm/ 1.46inch; Bottom diameter: 3cm/ 1.18inch 3.7-4.5cm: Height: 3.8cm/ 1.5inch; Top diameter: 4.5cm/ 1.77inch; Bottom diameter: 3.7cm/ 1.46inch 3-3.7cm Hole: Height: 3cm/ 1.18inch; Top diameter: 3.7cm/ 1.46inch; Bottom diameter: 3cm/ 1.18inch Package Includes:(3 Pack) 1 Piece Glassware Stopper