How to Use: 1. Rotate the bottle with light force to make a knife marking; 2. Jacket the rubber rings on both sides of the knife marking, pour boiling water and rotate the bottle for about 40 seconds; 3. Pour cold water and rotate the bottle for 20 seconds; 4. Gently break it and finish the job. Specification: Item Type: Glass Bottle Cutter Material: Stainless Steel Colour: Black Cutting Length Range: Approx. 6.5 ~ 16cm / 2.6 ~ 6.3in Cutting Diameter: Approx. 1.2 ~ 6cm / 0.5 ~ 2.4in Cutting Depth: Approx. 2mm / 0.1in Application: For cutting bottle. Package List: 1 x Glass Bottle Cutter 2 x Plastic Ring 1 x User Manual Note: It must be ensured that the bottle is empty and open, and it is forbidden to plug the bottle or cork. The mouth of the bottle just cut off is very incisive, please be careful not to cut your fingers! If you fail to cut and open the bottle, please repeat step two and step three.