Have you ever seen these abbreviations before, C/T, TW, T/O?

What do they mean?

If you’re like me, when I first started in the packaging world, a cap was a cap, there were no differences. It didn’t take long to figure out how wrong I was.

The two main types of finishes are Continuous Thread or C/T and Lug Twist-off or TW, T/O. What’s the difference? Is one better than the other? Well, let’s start with a quick side-by-side picture of a jar with a continuous thread finish and a lug twist-off finish.

Can you see the difference between the two?

The Continuous Thread or C/T closure-style neck finish has a thread that wraps all the way around the opening of the Jar or bottle without any breaks in the threading.

Continuous Thread finish are normally written out xx/400 or xx/450. For example, 70/450 Gold Metal Plastisol Lined Cap. The 70 refers to the opening diameter in millimeters that this closure fits on while the 450 refers to the thread style and depth. If the second number is in the 400 range then that closure will be a continuous thread cap.

The C/T closure, like the bottles and jars, also features a thread inside the cap. When the cap gets applied to the top of the container the ridge inside of the cap will follow the thread on the container and tighten down as it is spun around the top. These closures are the perfect choice if your hand applying the caps since you are able to tighten the cap all the way without stripping it.

Of course, there are many other factors involved in sealing a cap onto a jar besides screwing the lid on, so please test these closures with your product.

Lug Twist-off is a much different finish than continuous thread. The finish on the Jar or Bottle has breaks in the threading creating multiple threads around the opening of the container. Lug Twist-off finishes are typically written out either 53mm T/O or TW or 53-2020. The first number 53 corresponds to the opening diameter and the T/O or TW refers to “Twist”. The second number refers to the thread style or GPI (Glass Packaging Institute) Finish. If the second number is in the 2000 range then it will be a lug finish.

Lug caps are a little more difficult to apply than C/T caps and are more designed to be applied by a capping machine. They require a certain amount of torque to be applied to the cap to create that seal. Of course, you can still apply these caps by hand, but they typically require around a quarter turn when applying the cap. If you go too far then the cap is stripped and unusable.

Lug caps feature around 4 notches on the inside of the cap and when it is applied to the top of the container, the notches will follow the treading down and tighten.

These closures are cheaper than continuous thread caps, but you should definitely be careful if you’re applying them by hand.

If you would like to learn more about Continuous Thread and Lug finishes or have questions, please call us at (800) 903-2830 or email us at info@burchbottle.com. Our packaging experts are always ready to help.