OSK™ SAE Boss O-Ring Seal Kit K155X8N90-900 is a 155 piece Buna-N 90 Duro Boss O-Ring assortment for SAE 900 series straight thread tube fittings. This kit includes 8 popular Boss seal sizes used in hydraulic equipment repair and service. It helps maintenance shops, service trucks, and hydraulic repair teams keep common high-pressure Boss O-Rings organized and ready, reducing downtime and extra supply runs.
Benefits
The OSK™ SAE Boss O-Ring Seal Kit helps keep hydraulic repairs moving when Boss fittings need sealed fast. Instead of stopping work to search for one O-Ring, this kit keeps common 900 series Boss sizes in one organized case.
Key customer benefits include:
- Helps reduce downtime on hydraulic equipment
- Keeps popular SAE Boss O-Rings ready for repair work
- Supports faster fitting service and leak repair
- Reduces extra trips to the parts counter
- Helps service trucks stay prepared in the field
- Provides Buna-N 90 Duro O-Rings for higher pressure fitting applications
- Makes it easier to find the right Boss O-Ring during a repair
This kit is not just a box of O-Rings. It is a time-saving repair tool for shops and technicians who need common Boss seal sizes ready before the equipment is down.
Correct Size Coverage
This kit includes 155 total O-Rings in 8 popular SAE 900 series Boss seal sizes.
| Size | AS568 Dash Number | Tube Size OD | SAE Dash Size | Thread Size | Quantity |
|---|
| Boss O-Ring | -903 | 3/16" | -3 | 3/8-24 UNF | 15 |
| Boss O-Ring | -904 | 1/4" | -4 | 7/16-20 UNF | 25 |
| Boss O-Ring | -906 | 3/8" | -6 | 9/16-18 UNF | 15 |
| Boss O-Ring | -907 | 7/16" | Not provided | Not provided | 25 |
| Boss O-Ring | -908 | 1/2" | -8 | 3/4-16 UNF | 25 |
| Boss O-Ring | -910 | 5/8" | -10 | 7/8-14 UNF | 25 |
| Boss O-Ring | -912 | 3/4" | -12 | 1-1/16-12 UN | 15 |
| Boss O-Ring | -916 | 1" | -16 | 1-5/16-12 UN | 10 |
The 900 series dash numbers identify Boss seals used with straight thread tube fittings. Except for size -901, the digits after the 9 identify the nominal tube size in 16ths of an inch. For example, -904 is used for 1/4" tube, and -908 is used for 1/2" tube.
SAE, Metric, or Specialty Kit Type
This is an SAE 900 series Boss O-Ring seal kit.
It is made for Boss type straight thread tube fittings used in hydraulic equipment. This is not a general AS568 O-Ring assortment and it is not a metric O-Ring kit. It is built for customers who need common SAE Boss seal O-Rings for hydraulic fitting repair and service.
Material Compatibility
The O-Rings in this kit are Buna-N, also known as Nitrile or NBR.
Buna-N is a common material for hydraulic and shop repair because it works well with many petroleum-based fluids. It is often used with:
- Petroleum oils and fluids
- Hydraulic fluids
- Gasoline
- L.P. gases
- Cold water
- Silicone greases and oils
- Di-ester base lubricants
- Ethylene glycol base fluids
Buna-N is not recommended for every fluid. It should not be used with:
- Ketones such as MEK or acetone
- Phosphate ester hydraulic fluids such as Skydrol, Fyrquel, or Pydraul
- Halogenated hydrocarbons
- Nitro hydrocarbons
- Strong acids
- Automotive brake fluid
- Long-term ozone, sunlight, UV, or weather exposure
For critical applications, always confirm material compatibility with the fluid, temperature, pressure, and environment before use.
Durometer and Seal Performance
These O-Rings are Buna-N 90 Duro.
Durometer is the hardness of the rubber. A 90 Duro O-Ring is harder than the common 70 Duro general-purpose O-Ring. That added hardness can help with extrusion resistance in higher pressure fittings, which is why Buna-N 90 is often used for Boss O-Rings and hydraulic fitting seals.
A harder O-Ring can help support better seal life in the right gland and pressure range. It is still important to match the correct Boss size to the fitting. A wrong size or wrong material can still cause leaks, even when the O-Ring is high quality.
Best Uses
This Boss O-Ring kit is a strong fit for:
- Hydraulic repair shops
- Service trucks
- Farm and equipment repair
- Manufacturing maintenance
- Mobile hydraulic service
- Heavy equipment service
- Fleet maintenance
- OEM maintenance areas
- General hydraulic fitting repair
- Straight thread Boss fitting service
This kit is not ideal for unknown chemicals, critical aerospace, medical, or highly specified applications unless the required material, hardness, certification, and traceability are confirmed before use.
Quality and Reliability
This kit is built as a professional repair and maintenance solution. Customers get known sizes, known material, known hardness, and an organized selection of useful Boss O-Rings.
The customer benefit is simple. A better Boss O-Ring kit helps reduce wrong-size repairs, wasted time, and repeat leaks.
The O-Ring Store LLC is ISO9001:2015 certified, and we focus on practical seal solutions that help customers keep equipment working. When a fitting is leaking, the value is not only the O-Ring. The value is having the right seal ready when the repair needs to happen.
Organized Storage Case
The kit comes organized so Boss O-Rings can be stored by size and found faster during a repair.
That matters in a shop or service truck. When fittings are leaking and equipment is down, technicians need to find the right size quickly. Organized storage helps reduce mix-ups, wasted time, and repair delays.
Piece Count and Refill Value
This kit includes 155 total O-Rings across 8 common SAE 900 series Boss sizes.
The value is not just the total piece count. The value is having useful sizes in practical quantities for real hydraulic fitting repair work.
When a compartment runs low, customers can reorder replacement O-Rings from The O-Ring Store LLC instead of replacing the whole kit. That keeps the kit useful over time and helps control repair supply costs.
Price and Buying Value
This kit is a smart buy for shops and service teams that work with hydraulic Boss fittings.
A leaking fitting can stop equipment, slow production, and cost more than the O-Ring itself. Keeping common Boss seal sizes on hand helps prevent downtime, avoids last-minute supply runs, and keeps repairs moving.
For the customer, the value is speed, accuracy, and readiness. The right kit helps the team complete more repairs with less frustration.
Before You Buy
Before ordering, confirm that this kit matches the fitting style and size you need.
Check the following:
- Match the Boss O-Ring dash size to the fitting or original O-Ring
- Confirm the tube size, SAE dash size, and thread size when available
- Match Buna-N material to the fluid, temperature, pressure, and environment
- Do not assume all rubber materials work in every fluid
- For critical applications, confirm 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 clear sizing, practical product information, refill options, and support from a team that works with O-Rings and seals every day. The value is not just the kit. The value is speed, accuracy, service, and the ability to keep the kit working for the customer over time.
We are a small distributor that cares about helping customers get the right O-Rings without making the process harder than it needs to be.
FAQ
What is this O-Ring kit used for?
This kit is used for SAE 900 series Boss O-Rings on straight thread tube fittings, commonly found in hydraulic equipment.
Is this kit SAE or metric?
This is an SAE Boss O-Ring kit. It is not a metric O-Ring kit.
What material are the O-Rings?
The O-Rings are Buna-N, also called Nitrile or NBR.
What durometer are these Boss O-Rings?
These O-Rings are 90 Duro. This is a harder rubber commonly used for hydraulic fittings and higher pressure sealing.
Can I use this kit with hydraulic oil?
Buna-N is commonly used with petroleum-based hydraulic fluids. Always confirm compatibility for the exact fluid and operating conditions.
Can I refill the 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?
Check the fitting type, tube size, SAE dash size, thread size, and Boss O-Ring dash number. This kit includes -903, -904, -906, -907, -908, -910, -912, and -916.
