UL125-0.500-125B is a polyurethane loaded U-Cup seal with a Buna-N O-Ring energizer, sized for hydraulic rod or piston sealing where a tighter, more responsive seal is needed.
The UL125-0.500-125B High Performance Loaded U-Cup helps stop hydraulic leaks, restore cylinder performance, and reduce downtime by improving sealing force under pressure. The loaded design uses a polyurethane sealing body with a Buna-N energizer to help maintain lip contact, making it a strong choice for hydraulic cylinder repair, mobile equipment, and shop rebuilds.
This size is part of the Universal Rod/Piston U-Cup build list, and the reference table shows UL125-0.500-125B as the loaded version for the 1/8" X 1/2" X 1/8" size, fitting a 1/2" rod or 3/4" bore.
Operating Temperature
Operating temperature: -40° to +230°F (-40° to +110°C)
Material & Performance Details
This loaded U-Cup uses a polyurethane body for wear resistance, extrusion resistance, and reliable sealing in hydraulic service. The Buna-N O-Ring energizer helps preload the sealing lips, which can improve low-pressure sealing and maintain contact as pressure changes.
Polyurethane is a strong material choice for hydraulic seals because it handles abrasion, movement, and pressure better than many softer rubber seal designs.
- Excellent resistance to:
- Abrasion and wear
- Extrusion under pressure
- Petroleum-based hydraulic oils
- Dynamic cylinder movement
- Compression and deformation in properly designed glands
- Limited capability with:
- Some synthetic fluids
- High heat above the rated range
- Applications with poor rod or bore finish
- Not compatible with:
- Fluids that attack polyurethane or Buna-N
- Applications outside the temperature or pressure limits
Final compatibility should be verified against the hydraulic fluid, pressure, temperature, and equipment conditions.
Sizes & Measurements
- Dimensions: 1/2"ID X 3/4"OD X 1/8"HT
- Actual: 0.500"ID X 0.750"OD X 0.125"HT
- Metric: 12.70mm ID X 19.05mm OD X 3.18mm HT
- Part Number: UL125-0.500-125B
- Profile: Loaded U-Cup
- Seal Type: High Performance Loaded U-Cup Seal
- Rod Size: 1/2"
- Bore Size: 3/4"
- Cross Section: 1/8"
- Height: 1/8"
- Cross References: Not specified
Applications & Use Cases
The UL125-0.500-125B loaded U-Cup is used in hydraulic cylinders where the customer needs a dependable replacement seal for rod or piston sealing. It is commonly used in mobile hydraulics, agricultural equipment, construction equipment, dump trailers, forklifts, log splitters, presses, pumps, valves, industrial repair, MRO work, and hydraulic repair shops.
The customer benefit is simple. A correct fit means fewer leaks, faster repairs, less downtime, and more confidence when ordering replacement hydraulic seals.
Key Specifications
- Material: Polyurethane body with Buna-N O-Ring energizer
- Durometer: 95A Polyurethane, Buna-N energizer durometer not specified
- Color: Not specified
- Seal Type: Loaded U-Cup Seal
- Profile: High Performance Loaded U-Cup
- Application: Hydraulic cylinder rod or piston sealing
- Rod or Bore Use: 1/2" rod or 3/4" bore, depending on gland design
- Temperature Range: -40° to +230°F (-40° to +110°C)
- Pressure Rating: 0 to 5,000 PSI
- Surface Speed: Not specified
- Fluid Compatibility: Petroleum-based hydraulic fluid
- Certifications: Not specified
- Country of Origin: Not specified
- Brand or Manufacturer: Not specified
Why Buy from The O-Ring Store LLC
The O-Ring Store LLC helps customers get the right hydraulic seal faster, with less guessing and fewer wrong-part orders. We are ISO9001:2015 certified, stock products in the USA for fast delivery, and offer same-day shipping on in-stock items when order requirements are met. Our team can help identify seals by size, profile, and application, including custom and hard-to-find sizes. Lot traceability and documentation are available on request. We make getting O-Rings and hydraulic seals easy.
3 Most Common FAQs
FAQ 1: How do I know if this hydraulic seal will fit my cylinder?
Measure the seal ID, OD, and HT, then compare them to the rod size, bore size, and gland dimensions. This seal measures 0.500"ID X 0.750"OD X 0.125"HT. It is commonly matched to a 1/2" rod or 3/4" bore, depending on the gland design and whether it is used as a rod seal or piston seal.
FAQ 2: Can this seal be used as both a rod seal and piston seal?
This is a loaded U-Cup profile that may be used in rod or piston applications when the cylinder gland is designed for that style. Final use depends on the groove design, pressure direction, seal orientation, and cylinder condition.
FAQ 3: What information should I provide before ordering?
Provide the ID, OD, HT, material if known, fluid type, temperature, pressure, rod or piston use, equipment type, and clear photos of the old seal and gland if available. This helps reduce wrong-part orders and speeds up identification.
