At APM Hexseal, we specialize in the design and manufacture of sealing solutions. Equipped with over 70 years of industry experience, we have the knowledge and skills to develop high-performance sealing solutions for even the most extreme and volatile environments. One of our core product offerings is sealing hardware.

Sealing Hardware

Sealing hardware has a dual purpose. It is designed to fasten two or more components together while preventing essential process fluids from escaping and contaminants from entering. As a result, it helps maintain the integrity of the process material and the performance of the system, which can lead to greater productivity, longer uptime, and smaller maintenance and repair costs.

The following provides an overview of sealing hardware, outlining APM Hexseal’s:

  • Manufacturing Process

    How We Manufacture Our Sealing Hardware

    Our patented sealing technology is manufactured in two ways.


    Our Seeloc® washers and Seelnuts® are made using a proprietary metal-to-rubber bonding process. The process involves mechanically bonding rubber sealing components to the washers and nuts during the molding process. As a result, the sealing components are better able to maintain their integrity when fasteners are inserted or screwed into the hardware. Combining the fastening and sealing components into a single part also helps reduce manufacturing time, installation requirements, and the risk of failure.


    Our Seelskrews® and Seelbolts® feature a groove built into the underside of the fastener head. Once the fastener is formed, we insert an elastomeric O-ring into the groove tailored to meet the requirements and restrictions of the intended application. Since these fasteners do not need to be cut or grooved to create a space for the sealing components, they are able to form a solid seal without sacrificing their inherent structural integrity.

    Sealing Hardware Infographic

    For nuts and washers, the specifications of the rubber-to-metal bonding process vary based on the application for which the sealing component is created. Process temperature, pressure, and curing time should be tailored to ensure a strong bond in the final product. For screws and bolts, it is important to consider the size of the groove. It should be large enough to hold the O-ring needed for the application but small enough to not damage the integrity of the product.

  • Key Benefits

    Benefits of Sealing Hardware

    Our sealing hardware offers a number of benefits when used for fastening applications, such as:

    Greater Durability

    Hostile environments put a significant amount of strain on machinery. Sealing hardware helps protect equipment from damage and degradation, ensuring it continues to operate properly and efficiently. However, it must be able to withstand the conditions of the application.

    Our sealing hardware products are designed with reliability and durability in mind. They establish an impenetrable seal against a wide range of operating and environmental conditions, including the following:

    Sealing Hardware Solutions

    • Extreme Temperatures
      Our products are effective in both hot and cold conditions, maintaining their strength and durability in extremely high and low temperatures. This characteristic makes them suitable for use in a variety of equipment used in harsh environments, including for the construction, military, and research industries.
    • Oils and Chemicals
      Our sealing technology offers reliable protection against chemicals and oils. This characteristic makes them particularly useful for engines in vehicles and elevators, HVAC systems, lab equipment, and agricultural systems, all of which experience regular exposure to oils, coolants, fertilizers, and other harsh substances.
    • Food, Beverage, and Other Fluids
      Our sealing hardware prevents food, beverage, and other sticky or greasy compounds from entering machinery and interfering with operations.
    • Water and Weather
      The intrusion of water can wreak havoc on the sensitive internal components of industrial equipment. Our sealing products eliminate the risk of water intrusion in indoor and outdoor machinery ranging from construction vehicles to boating and marine equipment.
    • Dirt, Dust, and Sand
      The entrance of contaminants such as dirt, dust, and sand can severely impact the performance of a mechanical system. Our sealing technology prevents the ingress of particulates into indoor and outdoor industrial equipment, such as construction or military machinery.
    • Road Salt
      Road salts are highly corrosive to automobiles and other vehicles that come in contact with them. However, proper selection and installation of sealing hardware can protect the equipment from their corrosive effects.

    Better Pressure and Vibration Resistance

    In fluid systems, fasteners exposed to high internal and/or external pressures and vibrations may loosen over time. As a result, the seal formed may weaken, resulting in fluid leakage, pressure loss, and process material contamination. If left unchecked, these effects can lead to decreased process efficiency, reduced system performance, and lowered product quality.

    Our sealing products—particularly our sealing screws (Seelskrews) and bolts (Seelbolts)—are engineered for superior performance in environments with regular exposure to high impact, pressure, and vibration levels. Our customers know they can rely on our sealing hardware for their fastening and sealing needs.

    Smaller Investment Costs

    Our sealing hardware products are reusable. This quality makes them a cost-effective sealing solution as they can be installed, removed, and reinstalled without loss of performance. Over time, they can result in significant cost savings for our customers.

  • Manufacturer Selection Considerations

    Selection Considerations for Sealing Hardware Suppliers

    There are numerous manufacturers of sealing hardware. Choosing the right one to partner with is the key to finding the optimal sealing solution for an application. Some of the considerations to keep in mind when vetting potential partners include company experience and commitment to quality.

    At APM Hexseal, we’ve designed and manufactured environmental sealing solutions for over seven decades. Over our years in business, we’ve developed a reputation as a provider of innovative, strong, and reliable sealing products that meet or exceed customer expectations.

    Our team is dedicated to continuously improving the quality of our products and processes to achieve better and better sealing solutions. Currently, we maintain/comply with the following industry certifications and registrations:

    DEKRA Certified
    UL CertificationUL Certification
    Dodd-Frank Compliance
    REACH ComplianceREACH Compliance
    RoHS ComplianceRoHS Compliance

    APM Hexseal® Holds the Notable Distinction of Having Designed and Patented the Very First Self-Sealing Fasteners, Which Later Became Our Trademarked Seelskrews® and Seelbolts®

Our sealing product offerings include:

Socket Head Cap Screws

Socket Head Cap Screws

These screws feature a barrel-shaped head with a recessed hexagonal drive. The head is dimensionally smaller than most other standard screws, making it well-suited for confined areas of installation.

Seelskrews and Seelbolts

Seelskrews® and Seelbolts

These self-sealing fasteners create a reliable and reusable seal that prevents process fluids from escaping and contaminants from entering even in high impact, high pressure and highly demanding environments.

seelocSeeloc® Washers

Seeloc® Washers

Our washers consist of molded silicone rubber material bonded to stainless steel washers. They accommodate temperatures ranging from 103° to 400° F and internal and external pressures up to 100 psi. They can be used with any standard screws, bolts, and studs in sealing applications. We also offer a heavy-duty variation that exhibits at least 50% greater torque handling capacities.

Nutzilla 01


Like our other Seelnuts and sealing hardware, we use our proprietary metal-to-rubber bonding process to create Nutzilla. The single-piece design guarantees a nut that provides a consistent, reliable seal for ordinary large bolts without the need for additional gaskets or messy sealing compounds.



These self-sealing hardware products are one of our earliest innovations. They offer reliable performance in temperatures ranging from 103° to 400° F. They are compatible with standard screws, bolts, and studs, making them quick and easy to install in a variety of applications.

Contact the Sealing Experts at APM Hexseal for Your Sealing Hardware Needs

Founded in 1947 as a developer and manufacturer of environmental sealing solutions for electromechanical switches and circuits breakers in the military industry, APM Hexseal has since grown into an industry-leading provider of sealing products for extreme industrial and commercial applications. Available in multiple finishes and various locking options, our innovative sealing technology has revolutionized the hardware industry, combining effective sealing performance and easy installation and use requirements.

Regardless of your industry or application, the experts at APM Hexseal can provide an appropriate sealing solution for your needs. To learn more about our sealing hardware offerings or discuss your application requirements with one of our representatives, ask the experts today.