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The best sealing washer is the one specified for the connection—not a generic flat washer that happens to fit. Copper crush washers and metal-to-rubber bonded washers seal in different ways, so check the joint’s geometry, dimensions, fluid, service conditions and manufacturer instructions before buying.
What makes a sealing washer the right choice?
A sealing washer works as part of a particular joint. Its material and shape must match the surfaces it seals and the way the connection is assembled. A washer that fits over a bolt or thread is not necessarily the correct seal.
- Identify the equipment, fitting and connection type.
- Check the service documentation for the specified washer family and replacement instructions.
- Confirm the sealing faces, thread arrangement and washer dimensions.
- Match the washer materials to the fluid and operating temperature and pressure conditions.
There is no single best washer for every connection, and no universal pressure rating applies across washer types and constructions.
Which sealing washer types should you consider?
Copper crush washers
A copper crush washer seals by deforming as the connection is tightened. Copper washers are used in some specified drain-plug and banjo-bolt connections, but those examples do not make copper suitable for every plug or banjo fitting. Use one only when the equipment or fitting calls for a crush washer, and verify its inside diameter, outside diameter, thickness and seat.
#1 Best Overall
- Built for #8 Roofing Screws: Precision-sized inner diameter fits #8 screws tightly for secure, leakproof fastening on exterior projects.
- EPDM Bonded + 304 Stainless Steel: Durable 304 SS backing bonded with EPDM rubber provides long-lasting sealing and weather resistance.
- Waterproof & Weatherproof Seal: Blocks water, dust, and vibration—ideal for metal roofing, siding panels, pole barns, and outdoor structures.
- Reliable for Roofing & Self-Tapping Screws: Creates a flexible, strong seal on wood, metal, and plastic. Perfect for roofing screws and exterior fasteners.
- Contractor-Grade 100 Pack: Includes 100 bonded sealing washers in a resealable bag—built for roofers, builders, and serious DIY projects.
Reuse, torque and fitment requirements depend on the specific connection. Follow its service instructions rather than assuming that a copper washer can be reused or that a particular tightening method applies universally.
Bonded sealing washers
A bonded washer—also known as a Dowty seal—combines a metal carrier with a bonded elastomer sealing element. James Walker describes these seals for hydraulic equipment and other fluid systems, including fuel, pneumatic and HVAC or cooling applications. That broad range is not a blanket compatibility guarantee: the correct construction depends on the particular service conditions.
Rank #2
- High-quality materials: 378 rubber-to-metal combination o-ring gaskets in 12 sizes to meet virtually all your needs; high-quality NBR carbon steel seals provide excellent sealing, high-pressure, heat and abrasion resistance, and long service life
- Multiple Sizes: XBVV 378-piece adhesive seal kits include 12 different I.D. sizes, Φ6(6mm), Φ8(8mm), Φ10(10mm), Φ12(12mm), Φ14(14mm), Φ16(16mm), Φ18(18mm), Φ20(20mm), Φ22(22mm), Φ24(24mm), Φ27(27mm), Φ30(30mm)
- Widely used: Adhesive seal kits are perfect for all kinds of automobiles, electrical appliances, bearings, pumps, high pressure fuel systems, pumps, fuel line bolts and automotive replacement drain plug gaskets, etc
- Easy storage and use: various bonded sealing washers are placed in a sturdy plastic storage box, each size is labeled with a label paper and stored in order from small to large for easy access
- Quality service: XBVV always provides excellent customer service so you can buy with confidence.If you have any questions about the bonded sealing gasket set, please let us know and we will be happy to serve you
James Walker lists mild steel, stainless steel and aluminium bronze carriers, alongside NBR, HNBR, FKM and EPDM elastomers. Its product range includes BSP and metric size options and a stated temperature range of −40°C to +200°C. These are range-level details, not ratings that apply to every size or material combination; the manufacturer says performance parameters depend on construction. Check the specific product information at James Walker’s bonded seals and Dowty washers page.
Other washer materials
Fiber and polymer washers are also available, but the available application-specific information does not establish a particular connection for which to recommend them here. Choose them only when the equipment or fitting specification calls for that type.
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Rank #3
- FUNCTION: Daptemn 245pcs metric zinc-plated steel self-centred rubber seal washer combination box, is suitable for cars, ships, engines, oil pipelines, gas control, faucet seal repair with silicone seal washers
- INTERNAL SIZE: Assorted oil drain plug crush washer set internal diameter: M6 (6 mm / 0.24" ), M8 (8 mm / 0.35" ), M10 (10 mm / 0.39" ), M12 (12 mm / 0.47" ), M14 (14 mm / 0.55" ), M16 (16 mm / 0.63" ), M18 (18 mm / 0.71" ), M20 (20 mm / 0.79" ), M22 (22 mm / 0.87" ), M24 (24 mm / 0.94" ), M27 (27 mm / 1.06"), M30 (30 mm / 1.18")
- OUTER SIZE: Assorted o ring kit set outer diameter: M6 (9 mm / 0.35"), M8 (13 mm / 0.51"), M10 (15 mm / 0.59"), M12 (17mm/0.67"), M14 (19mm/0.75"), M16 (21mm/0.83"), M18 (24mm / 0.94"), M20 (27mm/1.06"), M22 (29 mm / 1.14"), M24 (31 mm / 1.22"), M27 (34.5 mm / 1.35"), M30 (37.6 mm / 1.48")
- SPECIFICATION: Bonded sealing washer has: M6 (25pcs ), M8 (25pcs ), M10 (25pcs ), M12 (25pcs ), M14 (25pcs ), M16 (20pcs ), M18 (20pcs ), M20 (20pcs ), M22 (20pcs ), M24 (15pcs ), M27 (15pcs ), M30 (10pcs ), a total of 245 pcs
- MATERIAL: NBR O-ring is made of zinc-plated steel gasket and rubber, with oil as medium, for sealing threaded pipe joints and plugs. The working pressure is 400KA/CM (39.2MPA), and the working temperature is between -30°C - 120°C. A washer is a part that is placed between the connecting piece and the nut
How to check fit and compatibility before ordering
- Identify the joint. Consult the equipment or fitting documentation and determine the intended sealing arrangement. For hydraulic connections, matching the thread alone does not prove that the washer will make the intended seal.
- Confirm the washer family and geometry. Check whether the specification calls for a copper crush washer, bonded washer or another type. Verify the thread and seat arrangement, as well as inside diameter, outside diameter and thickness where specified.
- Match the materials to the service. For a bonded washer, confirm both carrier metal and elastomer against the fluid, temperature and pressure conditions. Do not infer compatibility merely because a replacement looks like the old washer.
- Check assembly and service instructions. Use the manufacturer’s stated pressure and assembly limits, torque instructions and reuse or replacement guidance for that specific connection. If those details are not established, do not substitute a general rule.
How to compare washer options
Compare only products with enough manufacturer documentation for the intended application. Use these criteria to evaluate a candidate washer:
- Specified connection type and sealing geometry
- Inside diameter, outside diameter and thickness
- Sealing mechanism and washer family
- Fluid and temperature compatibility
- Pressure and assembly limits for the specific product
- Reuse or replacement instructions
A product listing that gives a thread size but omits the required seat, materials or service limits may not provide enough information to confirm a suitable match. Ask the equipment maker or seal supplier when the specification is unclear.
Quick Recap
Best Value
- WHAT YOU WILL GET :You will get 130pcs o-ring gasket washers in 10 different sizes ,including M6,M8,M10,M12,M14,M16,M18.M20,M22,M24. Metric specifications for range of household, hydraulic, industrial and pneumatic applications
- MATERIAL:Made of commercial grade Nitrile Butadiene Rubber (NBR) with carbon steel material. Good sealing, high pressure resistant, oil resistant, corrosion resistant, UV resistant, heat resistant, wear resistant.
- APPLICATIONS:Ideal washers replacement for Automobile, mechanical, electrical, cylinder, bearing, pump, water pipe, valve, Idler, oil pipeline system,automotive replacement drain plug gaskets etc.
- PACKAGE:This seal assortment kit comes in a plastic storage case for organization and portability,and comes with a dimension chart for distinguishing different sizes easily
- WARM REMINDS:Please double check the dimensions of these rubber washer before you place the order.
Rank #4
- MATERIAL: Made with high quality 304 Stainless Steel and neoprene, not easy to rust, Anti-moisture, Anti-oxiclation, corrosion resistant, acid/alkali resistance for indoor and outdoor use.
- PACKING QUANTITY: 200Pcs sealing waterproof washers 4 sizes: M4.2x12--50Pcs, M4.8x14--50Pcs, M5.5x16--50Pcs, M6.3x16--50Pcs.
- SUITABLE FOR: These waterproof gaskets are smooth, hard, and thick, suitable for self-drilling screws, and are widely used in electrical equipment, industrial machinery, construction, etc.
- PLASTIC HEAT SEAL PACKAGING: Practical and convenient of packing box, All of washers are packed in a durable and sturdy box, this box can be use for a storage box.
- DURABLE DIVIDED STORAGE CASE: All washers are packed in the box with size label and divider, easy to store and won't mix up.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
