How to Select the Right Size Cap for your Bottle
Everyone from consumers to scientists know that the cap on your bottle has to fit correctly to prevent leakage, evaporation and potentially dangerous spills. What many don’t know is how to make sure the cap is the right size for the bottle.
Before you select a cap, you need to know the correct size. Cap sizes are not interchangeable – a 28-400 cap will not fit properly on a bottle with a 28-410 neck finish. Cap sizes and the neck finish on a bottle have a unique system of measurements.
How are closures sizes defined?
Screw thread closure sizes are expressed in two numbers:
The first number refers to the diameter of the closure or bottle opening (in mm) and refers to the nominal diameter measured across the inside of the cap at the opening or the outer diameter of the bottle.
The second number represents the GPI thread finish and refers to the height of the cap and the style of threads on the cap and the container. GPI refers to the Glass Packaging Institute which standardized neck finishes many years ago for both glass and plastic containers.
For Example,a closure size of 28-230 has a diameter of 28mm and fits container with a 430 GPI thread finish.
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