O ring specifically sized for the Hex and Big Hex worms.  These worms have more volume than a standard stick worm, so a larger ring is required.
As with all our designs, we wanted to make it better.  These o rings have a softer durometer measurement of 50, whereas the typical mass produced o rings most sellers just stuff in bags are a durometer of 70.  What does this mean?  Not only are our o rings USA sourced, they are softer and a bit stretchier.  Less binding on the bait, and easier to position and use.  
This o ring appears big when you hold it by itself, but it fits both the Hex and Big Hex perfectly.