The plastic jar cap with a silicone sealing ring is suitable for regular mouth Mason jars.SpecificationJar Cap:Color: Material: Inner Diameter: Size: Sealing Ring:Color: Material: Thickness: Inner Diameter: Packing List:  x Jar Caps and x Sealing RingsAdvantageThe can cap is made of durable PP material with a silicone sealing ring. The edge of the Mason jar lid is designed with non-slip ribbing for easy opening and tightening of the jar cap. The jar lid has a good tightness to keep your contents fresh, and it is great for the wide-mouth jar to dry storing or freeze in the refrigerator.InstructionEasy to use - just install the caps on the jar mouth and tighten it to seal.NOTE: Make sure the right size you need before ordering. Manual measurement allows 1mm-2mm of error.