How to Measure a Continuous Thread (CT) Closure Finish Size
What Does a 24/410 Closure Finish Size Mean?
Continuous thread closure sizes are typically written in a format such as 24/410, which contains two measurements. The first number, 24, refers to the "T" dimension, which is the outside diameter of the bottle neck measured in millimeters. The second number, 410, refers to the thread finish, which indicates the height and thread style of the neck finish.
This numbering system is commonly used for continuous thread (CT) closures and helps ensure the correct match between a bottle and its cap.
Matching a Closure Finish to a Container
Matching a closure to a container: To accurately match a bottle or container to a closure, multiple key dimensions—H, S, I, E, and T—must be measured. Proper measurements ensure the correct fit, thread engagement, and orientation of the closure.
Measuring diameter: To measure the T dimension (thread diameter), place a ruler across the bottle mouth with the hook against the thread. Read to the outer edge of the thread on the opposite side of the mouth.
| H Dimension: The height of the neck finish. It is measured from the top of the neck to the point where the "T" dimension (diameter) extended downward intersects the container shoulder. |
| S Dimension: Measured from the top of the finish to the top edge of the first thread. The "S" dimension helps determine how a closure aligns on a bottle and the amount of thread engagement between the bottle and cap. |
| I Dimension: The inner diameter of the bottle neck. Specifications typically require a minimum "I" dimension to allow adequate clearance for filling tubes. Linerless closures with a plug or land seals, as well as dispensing plugs and fitments, require a controlled "I" dimension for a proper fit. |
| E Dimension: The outside diameter of the bottle neck. The difference between the "E" and the "T" dimensions, divided by two, determines the thread depth. |
| T Dimension: The outside diameter of the thread. The tolerance range of "T" dimension determines the fit between the bottle and closure. |
Continuous thread finishes are commonly used with a wide range of caps, dispensing closures, pumps, and sprayers depending on the product application.
Ask your sales rep for a ruler!
