Check out these ESP 12mm Pop-up Corks.
The cork balls are produced in a natural unfilled cork which has a heavily pitted surface. This helps the paste grip. Pop ups should generally be as buoyant as possible. This helps to lift the hook and to prevent miss takes and hook ejection. It’s recommended that you use no more than 2mm of past around the cork.
Cork ball are great they grantee to pop up a rig for extreme periods of time so when you feel like you’re on the fish and not quite sure if your bait is still buoyant because it’s been out there all night you don’t have to worry if its cork because it won’t lose its buoyancy.