QUESTION:

What is the difference between compression set suffix B2 and B3 in ASTM-D1056?

ANSWER:

B2 requires a maximum set of 25% B3 allows a maximum set of 35% – John Bonforte, Sr.

People who wanted to learn about ASTM-D1056 were also interested in referencing ASTM 1056 MRPC PRESENTATION 2009 [PDF] – Understanding ASTM D1056 – American Society For Testing Materials D1056 (ASTM D1056); and ASTM D 1056 Explained [PDF]

​What Is the Difference Between UL JMLU2 and JMST2?

When comparing UL JMLU2 and UL JMST2, the most important distinction is simple:

JMLU2 is the generic category for material properties, while JMST2 applies to a specific end-product application.

That difference matters because engineers, designers, and buyers are often not asking the same question.

Sometimes the question is:

“What can this material do?”

Other times the question is:

“Is this gasket acceptable in this specific application?”

Those two questions lead to two different UL paths.

This category covers elastomeric materials supplied in sheet form or as formed or cut gaskets. These gaskets are evaluated for use in specific end-product applications.

JMLU2: A Material-Based UL Category

According to Monmouth Rubber’s existing technical explanation, JMLU2 is the main gasket and seal category and covers elastomeric and composite gasket materials in a wide range of forms, including:

• O-rings
• seals
• shaft seals
• flexible cellular gaskets
• facings
• sheet materials
• special forms
• poured-in-place gaskets

In other words, JMLU2 is broad. It is intended to describe and evaluate the material itself, rather than limit the review to only one finished gasket design or one narrow end use. That is why Monmouth describes JMLU2 as the generic category for material properties.

What JMLU2 is really intended to do

Monmouth states that this category is designed to provide a profile of the material properties. UL investigates the material with respect to characteristics such as:

• tensile strength
• elongation
• compression set
• tensile set
• hardness
• low temperature performance
• retention of these properties after accelerated aging
• retention of these properties after exposure to various environments

That means JMLU2 is valuable because it helps define how a gasket or seal material performs before it is tied to one exact finished product.

Why that matters

A material-level category like JMLU2 helps engineers and product designers compare materials against performance needs. Monmouth explains that these properties help designers and engineers identify materials that meet their requirements and comply with the safety standards associated with their products.

So, from a practical standpoint, JMLU2 helps answer questions like:

• Does this material have the physical strength required?
• Will it retain important properties after aging?
• Can it hold up after environmental exposure?
• Is it a strong candidate for a sealing application before the final product is fully defined?

That is why JMLU2 is often the more useful category when the conversation starts with material selection.

Expanded Focus on JMLU2

If your goal is to add more detail around JMLU2, this is the strongest way to position it on the page:

JMLU2 is about the material profile

JMLU2 is not just a label. It is a way of identifying how a gasket or seal material has been investigated from a property and performance standpoint. Monmouth’s explanation makes clear that the category is structured around measurable characteristics such as strength, elasticity, hardness, compression behavior, low-temperature behavior, and property retention after aging and environmental exposure.

JMLU2 covers many gasket and seal forms

Unlike a narrow application category, JMLU2 spans many common sealing forms, from O-rings and shaft seals to flexible cellular gaskets, sheet materials, and poured-in-place gaskets. That breadth is important because it shows that JMLU2 is centered on the material class and its performance profile, not just one final gasket geometry.

JMLU2 helps earlier in the design process

Because JMLU2 is built around the material’s properties, it is especially useful when a design team is still determining what sealing material is appropriate. Monmouth notes that these investigated properties help engineers find materials that meet requirements and align with applicable safety standards.

JMLU2 can also support end-product needs

Monmouth also notes that materials in this category may be evaluated to specific end-product standard requirements as requested. That is an important point, because it shows JMLU2 is fundamentally material-based, but it can still be relevant to downstream product compliance needs when a customer or design requires that added connection.

JMST2: A Specific Application UL Category

Monmouth’s explanation of JMST2 is much more focused. It states that this category covers elastomeric materials supplied in sheet form or as formed or cut gaskets, and that these gaskets are evaluated for use in specific end-product applications.

That makes JMST2 narrower than JMLU2.

What JMST2 means in practice

JMST2 is less about building a broad material property profile and more about whether a gasket material, typically in sheet, formed, or cut-gasket form, is suitable for a defined end use. Monmouth’s wording is concise, but the implication is clear: the evaluation is tied to application context.

So while JMLU2 helps answer:

“What does this material look like from a properties standpoint?”

JMST2 is closer to:

“Is this gasket acceptable for this specific end-product use?”

The Difference in Plain English

A simple way to explain the distinction is this:

JMLU2

Material-focused
Used when the goal is to understand the general physical and performance characteristics of a gasket or seal material.

JMST2

Application-focused
Used when the gasket is being evaluated for a particular end-product application.

Side-by-Side Comparison

UL Category	Primary Focus	Typical Scope
JMLU2	Generic material properties	Broad gasket and seal material profile across multiple forms
JMST2	Specific end-product application	Sheet, formed, or cut gaskets evaluated for defined use

Why Customers Often Ask About JMLU2 First

For many buyers and design engineers, JMLU2 is the more important starting point because it gives a broader understanding of the sealing material itself. Monmouth’s description shows that JMLU2 covers the kinds of physical and environmental property data that matter when choosing a material for performance, durability, and compliance.

That makes JMLU2 especially useful when:

• a customer is comparing different gasket materials
• a design is still in development
• the final gasket geometry is not the only issue
• long-term performance matters
• the material must retain key properties after aging or exposure

Final Takeaway

The best way to understand the difference is this:

JMLU2 is the broader, generic UL category used to profile gasket and seal material properties.
JMST2 is the narrower UL category used when gasket materials are evaluated for a specific end-product application.

Or, even more simply:

JMLU2 qualifies the material.
JMST2 qualifies the use.

 

Need help choosing the right UL-listed gasket material?
Monmouth Rubber can help you identify the right closed-cell sponge, sheet material, or fabricated gasket for your application and compliance requirements.

Contact Monmouth Rubber for technical support or material guidance.

HOW TO FIND OUR UL LISTINGS

On any browser, go to: https://iq.ulprospector.com/en

If you don’t have an account, we suggest creating one using your email.

In the search bar, enter “Monmouth Rubber”. This will provide a list of our different file listings:

Click on any of the Document Name links, e.g., JMLU2.MH10200 will take you to the next information page:

If you click on any of our stock numbers, e.g., DK1111, it will take you to the next section with even more information that can be useful for your evaluation.

The difference between UL Listed and UL Recognized

A UL listing is for finished end-user products. UL Recognized is for materials (called Components within UL) that can be used to be part of a UL listed product.

In other words, a UL listed product is the final product, whereas a UL Recognized product is a component of the final product. For a product to be UL listed, it needs to be UL evaluated, and its components must be UL Recognized.

The logos for UL Listed and UL Recognized are different:

The information provided above can be overwhelming and extensive, and we know it can generate subsequent questions for a particular application, for further information, we have implemented our “Ask John” technical service program, which is Monmouth’s global technical support service. It’s free & brings real value to your company.

It allows Monmouth’s customers and visitors to have a 24/7 Technical Library & Test Lab, absolutely free.

Have a technical question or problem, just call or email & “Ask John“

– John Bonforte, Sr.

QUESTION:

What is R factor?

ANSWER:

R factor is thermal resistance; a number denoting the resistance a material or system offers in the flow of heat, ft.2-°F-h/Btu – John Bonforte, Sr.

Understanding the Difference Between Short Ton, Long Ton, Metric Ton, and Imperial Ton

The word “ton” is often used as a general term for a large amount of weight, but in practice it can refer to multiple distinct units of measurement. These units are not equal, and misunderstanding them can lead to errors in manufacturing, shipping, and material specifications.

The most commonly referenced types are:

• Short Ton
• Long Ton
• Metric Ton (Tonne)
• Imperial Ton

While some of these terms overlap, each has a specific definition and historical context.

Short Ton

The short ton is the standard ton used in the United States.

• Weight: 2,000 pounds
• Equivalent: 907.18 kilograms

This unit comes from the U.S. customary system, where one ton equals 20 hundredweight, and each hundredweight equals 100 pounds.

Typical Applications

• U.S. manufacturing and production
• Construction materials
• Domestic freight and logistics
• Industrial materials such as rubber, polymers, and metals

In most U.S. industrial settings, “ton” without further qualification means short ton.

Long Ton

The long ton is a unit from the British Imperial system and is sometimes informally referred to as the British ton.

• Weight: 2,240 pounds
• Equivalent: 1,016.05 kilograms

The long ton is calculated using Imperial hundredweight, where one hundredweight equals 112 pounds. Twenty hundredweight equal one long ton.

Typical Applications

• Historical British measurements
• Maritime and naval contexts
• Legacy engineering and shipping documentation

Although no longer widely used in modern trade, the long ton still appears in specialized or historical references.

Imperial Ton

The Imperial ton is closely related to the long ton and, in most contexts, the two terms refer to the same unit.

• Weight: 2,240 pounds
• Equivalent: 1,016.05 kilograms

Key Clarification

In the Imperial system, the term ton specifically means long ton, not short ton. As a result:

• Imperial ton = Long ton
• Both are based on the 112-pound hundredweight
• Both total 2,240 pounds

The term Imperial ton is often used when distinguishing British Imperial measurements from U.S. customary units, particularly in international or historical discussions.

Where You May See It

• Older British technical standards
• Ship displacement and naval specifications
• Historical trade, mining, and infrastructure documents

Understanding this equivalence is important because some documents may use Imperial ton and long ton interchangeably.

Metric Ton (Tonne)

The metric ton, also called a tonne, is the standard ton used in the metric system and most of the world.

• Weight: 1,000 kilograms
• Equivalent: approximately 2,204.6 pounds

Unlike the short and Imperial/long tons, the metric ton is directly tied to the International System of Units (SI), making it consistent and universally accepted in global manufacturing and trade.

Typical Applications

• International shipping and logistics
• Manufacturing and engineering
• Scientific and technical documentation
• Global material specifications

Comparison Table

Ton Type	Pounds	Kilograms	Measurement System
Short Ton	2,000 lb	907.18 kg	U.S. Customary
Long Ton	2,240 lb	1,016.05 kg	British Imperial
Imperial Ton	2,240 lb	1,016.05 kg	British Imperial
Metric Ton	2,204.6 lb	1,000 kg	Metric (SI)

Why These Distinctions Matter

Because the difference between these units can exceed 200 pounds per ton, failing to specify the correct ton type can lead to:

• Incorrect material quantities
• Pricing and contract discrepancies
• Shipping weight errors
• Production and engineering miscalculations

In industries that deal with bulk materials—such as rubber manufacturing and industrial components—precision in weight terminology is essential.

Best Practice for Industrial Use

To avoid confusion:

• Always state the specific type of ton
• Include pound or kilogram equivalents
• Use metric tons for international documentation whenever possible

Clear definitions ensure accurate communication across suppliers, customers, and global partners.