The airlock cork is a number 6 1/2 rubber stopper. Also referred to as a Bung. There is a drilled hole in the center to mount the airlock, which goes through the entire length of the stopper.

Drilled to accept airlock or tubing.

Dimensions

Top diameter: 50mm, 1.97 inches. Bottom diameter: 42mm, 1.65 inches

Seals & Holds - This tapered rubber stopper provides a better seal as well as holds the airlock in place.  

Will not fall through the drilled hole - The Tapered bottom of the cork will not allow it to fall through the hole when the proper diameter hole is drilled.  

The 6.5 rubber stopper will fit perfectly into a hole drilled 1 1/8” inches in diameter.  

Very Commonly Used Rubber Stopper - Can also receive tubing directly to the drilled hole.  This will also allow you to use the stopper as one piece of a blowoff.

Easy to Clean & Sanitize - Can be used with commonly used cleaning sanitizing solutions.