The thread profile is one of the most critical and misunderstood aspects of effective closure design. Selecting the right thread profile can mean the difference between a high-quality closure and a closure that does not meet your needs. Each thread profile serves a specific purpose, so it’s important to understand the differences between them.

What is a Thread Profile? 

Imagine cutting a cap in half and looking at the threads from the side. The angle and depth of the threads in that cross section are what we call the thread profile. At Reliable Caps, we offer two different kinds of thread profiles: the “L” style, and the “M” style. Each profile has different benefits and drawbacks, and selecting the right one depends on multiple factors. For the most part, choosing your thread profile is not related to the contents of the bottle (save a few exceptions) or the “security” of the cap. Instead, it mostly has to do with the bottle’s mold and material. Picking the right thread profile for your bottle is essential for ensuring that your closure has a strong fit with low risk of leakage. 

What is an “L” or Standard Thread Profile?

Our first type of thread profile is the “L”, or Standard Thread Profile. This thread profile has a 30-degree thread contact surface and is used for a wide variety of products, from agriculture to food products and beyond. The Standard “L” style thread profile is less expensive, easier to make, and easier to line, so it is a great choice for many different kinds of closures, especially for bottles with newer molds or made out of materials like PET (polyester). 

These thread profiles are also slightly less precise than the “M” style. Luckily, newer bottle molds require less margin for error, and therefore “L” style threads are still a great option for newer bottle molds and precise materials. 

What is an “M” or Modified Buttress Thread Profile? 

The second thread profile we offer at Reliable Caps is the “M” profile, or the Modified Buttress. Our modified buttress thread profile has a 10-degree thread contact surface. “M” style thread profiles are stronger than the “L” style and can be used for a wide variety of caps, but are most commonly used for larger or heavier bottles, such as 2.5-liter bottles or older bottle molds.  

While the “L” style is more modern and easier to make and line, the “M” style provides a more secure fit, and allows for more margin of error on older bottle molds. The high contact surface between the thread on the bottle and the thread on the cap also provides better back-off resistance, which is great for bottles with more aggressive chemicals to help prevent leaking and back-off.  While other cap companies have abandoned the modified buttress because it is much more difficult to manufacture, we still make these caps for clients that are looking for this style of closure. You can even request this style thread in a different resin to provide an additional level of protection during transportation for products that go through extended shipping processes.

How Do I Select the Right Thread Profile?

The benefits and disadvantages that we’ve outlined for each type of thread profile can get you started as you consider your specific closure needs. If you have any questions, or just want some extra help guiding you through the decision-making process, we are always here to offer personalized assistance with your closure orders. No matter how small or large your order, we promise that it will always get to you with the shortest possible lead time, without sacrificing quality. Contact us to discuss your cap needs.