Flight-critical and defense systems leave no margin for leakage, weight penalties, or maintenance-driven failure. SFC KOENIG expander plugs, restrictors, and check valves deliver lightweight, high-integrity sealing and flow control engineered to meet the strictest safety and qualification standards.
KOENIG EXPANDER® plugs seal landing gear, hydraulic actuator, and engine housings; KOENIG RESTRICTOR® components regulate flow in flight control hydraulics, fuel systems, and propeller controls; KOENIG CHECK VALVE® solutions manage flow in engine, cabin, and environmental control systems — securing precise, repeatable performance throughout the aircraft lifecycle.
The same field-proven sealing and flow control principles protect hydraulic and fluid systems in defense vehicles, platforms, and equipment operating in demanding, mission-critical environments where reliability is non-negotiable.

Sleeve: Stainless steel
Ball: Stainless steel
Pressure to max. 450 bar
Size: From ∅ 3.0 to 14.0 mm

Sleeve: Stainless steel
Ball: Stainless steel
Pressure to max. 450 bar
Size: From ∅ 0.093 to 0.281 inch

Sleeve: Stainless steel
Ball: Bearing steel
Pressure to max. 450 bar
Size: From ∅ 3.0 to 22.0 mm

Sleeve: Case hardened steel zinc plate
Ball: Bearing steel
Pressure to max. 350 bar
Size: From ∅ 3.0 to 22.0 mm

Sleeve: Aluminium
Ball: Stainless steel
Pressure to max. 210 bar
Size: From ∅ 3.0 to 12.0 mm

Sleeve: Aluminium
Ball: Stainless steel
Pressure to max. 210 bar
Size: From ∅ 0.156 to 0.437 inch

Sleeve: Aluminium
Ball: Stainless steel
Pressure to max. 150 bar
Size: From ∅ 0.125 to 0.406 inch

Sleeve: Stainless steel
Ball: Stainless steel
Pressure to max. 350 bar
Size: From ∅ 4.0 to 10.0 mm

Sleeve: Stainless steel
Ball: Stainless steel
Pressure to max. 350 bar
Size: From ∅ 0.156 to 0.375 inch

Sleeve: Stainless steel
Ball: Stainless steel
Pressure to max. 250 bar
Size: From ∅ 0.125 to 0.281 inch

Sleeve: Case hardened steel
Ball: Heat treatable steel
Pressure to max. 500 bar
Size: From ∅ 4.0 to 12.0 mm

Sleeve: Case hardened steel
Ball: Heat treatable steel
Pressure to max. 500 bar
Size: From ∅ 4.0 to 10.0 mm

Sleeve: Stainless steel
Ball: Stainless steel
Pressure to max. 60 bar
Size: From ∅ 4.0 to 10.0 mm

Sleeve: Case hardened steel
Ball: Steel
Pressure to max. 60 bar
Size: From ∅ 4.0 to 20.0 mm

Material: Stainless steel
Cracking Pressure: 0.14 to 2.00
Max. Working Pressure in Check Direction: 280 bar
Size: Ø 5.5mm

Material: Stainless steel
Cracking Pressure: 0.14 to 2.00
Max. Working Pressure in Check Direction: 280 bar
Size: Ø 5.5mm

Material: Stainless steel
Cracking Pressure: 0.14 to 1.00
Max. Working Pressure in Check Direction: 280 bar
Size: Ø 8.0mm

Material: Stainless steel
Cracking Pressure: 0.14 to 1.00
Max. Working Pressure in Check Direction: 280 bar
Size: Ø 8.0mm

Material: Stainless steel
Max. Working Pressure in Check Direction: 210 bar
Size: From Ø 4.0 to 10.0 mm