Download our guide - Closures don’t usually fail because the cap is “bad.”They fail because the neck finish wasn’t clearly defined in the first place. If you work with bottles, closures, or packaging specs—this one’s for you. Why the Bottle Neck Is a Big Deal That small area at the top of the bottle controls: Seal integrity Torque performance Leak resistance Drop test survival Consumer opening experience And yet… it’s often reviewed last. By the time leakage shows up in test