OSK™ SAE Boss O-Ring Seal Kit K250X12N90-900 includes 250 Buna-N 90 Duro O-Rings in 12 common SAE 900-series Boss sizes. This kit is made for hydraulic repair, service trucks, maintenance shops, and equipment repair teams that seal straight thread tube fittings. It helps reduce downtime by keeping common Boss O-Ring sizes organized, ready, and easy to find during repairs.
Benefits
The OSK™ SAE Boss O-Ring Seal Kit helps shops repair hydraulic fittings faster with less guesswork. Instead of searching for one O-Ring at a time, the customer has the most common Boss seal sizes ready in one organized kit.
Key customer benefits include:
- Helps reduce downtime on hydraulic repairs
- Keeps common SAE Boss O-Rings on hand
- Saves trips to the parts counter
- Helps service trucks stay ready for field repairs
- Supports faster repair decisions
- Uses harder Buna-N 90 Duro material for high-pressure fitting applications
- Helps reduce wrong-size repairs by organizing sizes by Boss dash number
This kit is not just a box of rubber O-Rings. It is a repair tool that helps keep equipment, service work, and shop jobs moving.
Correct Size Coverage
This kit includes 250 O-Rings in 12 popular SAE 900-series Boss sizes. Boss O-Rings are commonly used to seal straight thread tube fittings in hydraulic equipment.
| Size | AS568 Boss Dash Number | Tube OD | Thread Size | Quantity |
|---|
| SAE Boss O-Ring | -904 | 1/4" | 7/16-20 UNF | 35 pcs |
| SAE Boss O-Ring | -905 | 5/16" | 1/2-20 UNF | 30 pcs |
| SAE Boss O-Ring | -906 | 3/8" | 9/16-18 UNF | 30 pcs |
| SAE Boss O-Ring | -907 | 7/16" | Not listed | 25 pcs |
| SAE Boss O-Ring | -908 | 1/2" | 3/4-16 UNF | 25 pcs |
| SAE Boss O-Ring | -909 | 9/16" | Not listed | 20 pcs |
| SAE Boss O-Ring | -910 | 5/8" | 7/8-14 UNF | 20 pcs |
| SAE Boss O-Ring | -911 | 11/16" | Not listed | 15 pcs |
| SAE Boss O-Ring | -912 | 3/4" | 1-1/16-12 UN | 15 pcs |
| SAE Boss O-Ring | -913 | 13/16" | Not listed | 15 pcs |
| SAE Boss O-Ring | -914 | 7/8" | 1-3/16-12 UN | 10 pcs |
| SAE Boss O-Ring | -916 | 1" | 1-5/16-12 UN | 10 pcs |
The size mix is strongest in the smaller and mid-range Boss O-Rings that are often used in hydraulic service and equipment repair.
SAE, Metric, or Specialty Kit Type
This is an SAE Boss O-Ring kit. It is made for SAE 900-series Boss seals used on straight thread tube fittings.
This is not a general AS568 O-Ring kit and it is not a metric O-Ring kit. It is a specialty hydraulic fitting kit for Boss-style sealing applications.
Material Compatibility
The O-Rings in this kit are made from Buna-N, also called Nitrile or NBR. Buna-N is a common material for hydraulic repair because it works well with many petroleum-based oils, fuels, and hydraulic fluids.
Buna-N 90 is commonly used for:
- Petroleum oils
- Hydraulic oils
- Gasoline and many fuel applications
- L.P. gases
- Silicone greases
- Water in some applications
- Ethylene glycol base fluids
- Di-ester base lubricants
Buna-N is not recommended for:
- Phosphate ester hydraulic fluids such as Skydrol, Fyrquel, and Pydraul
- Automotive brake fluid
- Strong acids
- Ketones
- Halogenated hydrocarbons
- Long-term ozone, UV, or weather exposure
Temperature range:
- -40°F to +250°F
- -40°C to +121°C
Always confirm material compatibility for critical applications. Fluid, pressure, temperature, and exposure can change seal performance.
Durometer and Seal Performance
This kit uses 90 Duro Buna-N O-Rings.
Durometer means hardness. A 90 Duro O-Ring is harder than a standard 70 Duro O-Ring. That matters in hydraulic fittings because a harder O-Ring can help resist extrusion when pressure is higher.
90 Duro is often used for:
- Hydraulic fittings
- Boss O-Rings
- Higher-pressure sealing points
- Applications where extra extrusion resistance is needed
The harder material helps the O-Ring hold its shape better under pressure. This can improve seal life when the size, material, and application are correct.
Best Uses
This kit is a good fit for:
- Hydraulic repair shops
- Service trucks
- Farm and equipment repair
- Manufacturing maintenance
- Mobile equipment repair
- Industrial maintenance teams
- OEM maintenance areas
- Fleet repair shops
- Hose and fitting service counters
- Field repair kits
This kit is not ideal for unknown chemicals, aerospace, medical, or highly specified applications unless the required material, hardness, certification, and traceability are confirmed before use.
Quality and Reliability
The OSK™ SAE Boss O-Ring Seal Kit is built as a professional repair and maintenance solution. The value comes from having the correct style of O-Ring, known material, known hardness, and useful size coverage in one organized kit.
A better kit helps reduce:
- Wrong-size repairs
- Wasted repair time
- Repeat failures
- Delays from missing common sizes
- Extra supply runs during urgent jobs
The O-Ring Store LLC is ISO9001:2015 certified. That matters because customers need dependable O-Rings, clear information, and support from a team that works with O-Rings and seals every day.
Organized Storage Case
This kit keeps SAE Boss O-Rings organized so the customer can find the right size faster during a repair.
An organized case helps:
- Keep sizes separated
- Reduce mix-ups
- Speed up field repairs
- Make service trucks easier to stock
- Help technicians see when a size is running low
Fast size selection matters when equipment is down and the customer needs the repair completed quickly.
Piece Count and Refill Value
This kit includes 250 total O-Rings across 12 popular SAE Boss sizes.
The value is not only the total piece count. The value is having useful sizes in useful quantities. Smaller Boss sizes are included in higher quantities because they are often used more often in service work.
When a compartment runs low, customers can reorder replacement O-Rings from The O-Ring Store LLC. That helps keep the kit working over time without replacing the entire assortment.
Price and Buying Value
This kit is a smart purchase for shops and service teams that work with hydraulic fittings. One delayed repair can cost more than keeping the right O-Rings on hand.
The customer benefit is simple:
- Less downtime
- Fewer emergency supply runs
- Faster hydraulic fitting repairs
- Better organization
- More confidence that common Boss sizes are ready when needed
This kit helps customers keep repairs moving instead of stopping work to find a single O-Ring.
Before You Buy
Before ordering, confirm the O-Ring size and material needed for your repair.
Check the following:
- Match the Boss dash size to the fitting
- Match the tube OD and thread size when available
- Confirm the material works with the fluid
- Confirm the temperature range is correct
- Confirm pressure and extrusion requirements
- Do not assume all rubber materials work in every fluid
For critical applications, confirm the required material, hardness, certification, and traceability before use.
Why Buy From The O-Ring Store LLC
The O-Ring Store LLC is an ISO9001:2015 certified O-Ring and seal distributor. We make getting O-Rings easy.
Customers get more than a kit. They get clear sizing, practical product information, refill options, and support from a team that works with O-Rings and seals every day.
The value is speed, accuracy, service, and keeping the kit useful over time.
FAQ
What is this O-Ring kit used for?
This kit is used for sealing SAE Boss straight thread tube fittings in hydraulic systems.
Is this kit SAE or metric?
This is an SAE Boss O-Ring kit. It includes 900-series Boss O-Ring sizes, not metric sizes.
What material are the O-Rings?
The O-Rings are Buna-N, also called Nitrile or NBR.
Can I use this kit with hydraulic oil?
Buna-N 90 is commonly used with many petroleum-based hydraulic oils. Always confirm compatibility with the exact fluid.
What does 90 Duro mean?
90 Duro means the O-Ring is harder than standard 70 Duro material. It is often used for hydraulic fittings and higher-pressure sealing.
Can I refill this kit?
Yes. Replacement O-Rings can be reordered from The O-Ring Store LLC when common sizes run low.
How do I know if this kit has the size I need?
Match your Boss dash number, tube OD, and thread size to the size chart before ordering.
