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Copper sealing washers, M21, 25 pack, plain finish

Zoro Select

Zoro Select M50301.210.0028 Copper Sealing Washer M21 25 Pack

SKU CH-XQJN-F0PXG

Copper sealing washers for M21 bolts, 21 mm inner and 28 mm outer diameter, 1.5 mm thick, pack of 25

  • Product typeWashers
  • Copper construction resists corrosion in fluid systems
  • 25 washers per pack cover multiple service jobs
  • 21 mm inner diameter fits M21 bolts precisely
  • 28 mm outer diameter distributes clamping force evenly
  • 5 mm thickness with ±0.2 mm tolerance ensures consistent sealing

Copper M21 sealing washers

These copper sealing washers fit M21 bolts and come in a pack of 25. Each washer has a 21 mm inside diameter and a 28 mm outside diameter with a uniform 1.5 mm thickness. The annealed copper construction provides reliable sealing for fluid or gas connections in automotive and industrial assemblies.

Consistent seal under torque

The annealed copper material deforms evenly when tightened to create a uniform seal that maintains integrity under sustained vibration and pressure cycling. Unlike composite washers that can extrude or harden over time, the solid copper construction resists creep and retains its sealing force throughout repeated thermal expansion cycles.

Low thermal resistance and clean installation

Copper conducts heat efficiently away from the joint which helps prevent localised hot spots in high-temperature fluid systems. The plain finish requires no additional surface preparation and produces no particulate debris during installation. Each washer weighs very little so the pack adds minimal mass to the assembly.

How it compares

Measured against everything we stock in General Hardware & Accessories, at today’s prices. Recalculated every night.

Price $9.99
Cheaper than about 80% of the 2,607 comparable items (median $18.99).

Specifications

Product
Brand nameZORO SELECT
Product typeWashers

Questions about this item

Do these copper washers deform permanently after repeated heat cycles in an exhaust system?

Copper is annealed for ductility so it conforms when first torqued, but repeated thermal cycling will work-harden the material and reduce its ability to reseal on subsequent assemblies.

What thread specification must the M21 bolts or studs follow for these washers to seal correctly?

The washers are dimensioned for metric M21 fasteners with a 21 mm inside diameter and 28 mm outside diameter; they require standard coarse-pitch M21 threads to sit flat and compress evenly.

Can the 25-piece pack cover both cylinder-head and manifold flanges on a typical inline-four engine?

An inline-four usually has eight to twelve exhaust flange joints, so the 25 washers provide enough for a full gasket refresh with spares left over.

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