Expander Plugs - All About KOENIG EXPANDER® Products

The KOENIG EXPANDER plug is designed to effectively seal drilled holes in fluid systems. With more than 5 billion parts installed and field failure rates less than 1 PPM, these plugs provide proven performance and an industry-leading metal-to-metal seal solution.

Compared to other expander seal options, KOENIG EXPANDER plugs consistently exceed performance expectations, providing a precise and reliable solution, often at the lowest total cost. These plugs feature a one-piece, easy-to-install design that integrates with automated manufacturing operations, and are available in a wide range of material options and plug sizes.

KOENIG EXPANDER components tolerate one of the widest temperatures ranges of any expander plug option in the market, with effective operation from -40°C to 150°C (-40°F to 302°F). Push-style expander models and pull-style expander seal models permanently resist pressures up to 450 and 550 bar, and are pressure rated with safety factors to accommodate system shocks and pressure spikes.

The KOENIG EXPANDER plug is one of the most dependable and customizable expander seals in the market and can be custom-configured to meet the needs of virtually any application.


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KOENIG EXPANDER plugs use our unique metal-to-metal seal design, which eliminates the potential for leaks commonly associated with other traditional expander seals, such as O-rings and gaskets.

With a one-piece design, KOENIG EXPANDER® products provide clean fit and reduce the risk of installation errors. These expander seals eliminate the need for customer assembly, thread machining, tapping or reaming, providing significant savings in labor and production process costs while also removing the risk of contamination from metal chips or debris.

In addition, the design does not require additional sealant or adhesive compounds, which further eliminates contamination risks. Ideal for a wide variety of applications, SFC KOENIG’s plugs are well-suited for deep-holes, angled channels and uniquely-oriented installations.


Two designs are available: a push style and a pull style. The difference between the two is mostly dependent upon the installation method.

Push-style models require a hole drilled with a counter bore. The plug is dropped into the hole up to the counter bore and then a ball is pressed into a seated shell, which causes serrated grooves to expand into the base material creating a tight, metal-to-metal seal. View our line of Push-Style plug products. >>

Pull-style models do not require the hole to be counter-bored and instead use an integrated mandrel to insert the plug into a drilled hole. Since it can be easily aligned, the pull-style plug is often used for angled channels. This style of expander plug is also ideal for applications where holes are on different faces and it is difficult to move the block for proper orientation. View our line of Pull-Style KOENIG EXPANDER plug products. >>

Design Support

Our expertise is at your service. Speak to our engineers for complete design-in support of our sealing and flow control solutions.

Installation Equipment

SFC KOENIG offers a complete line of installation equipment including hydropneumatic systems, handheld tools and setting components.