Loaded U-Seals

Request A Quote

Loaded USeals

U-seals & U-cup Applications

U-seals, or U-cups, are used in rod or piston applications (symmetrical U-seals can be used in either application). Loaded U-seals or U-cups, sometimes called Polypaks, are loaded with an O-Ring, or sometimes a quad ring, between the two lips to increase the sealing force at low pressures.

U Cup Seal Design

These type of parts are relatively soft, non-metallic rings, placed in a groove or fixed in a combination of rings, forming a seal assembly. This assembly is used to block or separate fluid in reciprocating motion applications. Hydraulic seals use is critical in providing a way for fluid power to be converted to linear motion.


Hydraulic seals can be made from a variety of materials such as polyurethane, rubber or PTFE (a generic compound of Teflon™, a trademark of The Chemours Company). The type of material is determined by the specific operating conditions or limits due to fluid type, pressure, fluid chemical compatibility or temperature.

A static seal is located in a groove and sees no movement, only sealing within its confined space

Loaded U-seals come in the following common styles:

  • RTUB standard loaded rod seals
  • Standard Loaded U-seals
  • Deep Loaded U-seals
  • B-Type Loaded U-seals

U-seals are available in standard and metric sizes.

We offer same-day shipping for many parts and perform quality checks of every order, so you know your critical parts will meet your application specifications.

Contact Rocket Seals today to see how we can help solve your sealing challenges.

Get A Quote


If you have any questions, please fill out the form below and a Rocket Seals technical expert will get in touch with you shortly.

Yes, sign me up.

Need O-Rings or Other Seals Fast?


Rocket Seals is the leading distributor for O-Rings and many other seals.

Request a quote and have it shipped the same day!

Request A Quote