M12 flat washer (Form C, large OD) in A4 stainless steel (316 marine grade) to BS4320-C. The large outer diameter spreads load over a wider area than a standard Form A washer - useful for oversized holes and soft parent materials. A4 (316) resists saltwater and chloride attack for coastal and marine use. Free next-day UK delivery on orders over £50.
  • M12 flat washer Form C marine grade 316 BS 4320
  • BS 4320 Form C flat washer M12 A4 marine grade stainless steel, side profile
  • Flat washer face-on - M12 A4 stainless Form C BS 4320
  • Simfix product label - 125CA4130PK25-SIM
  • Simfix product label - 125CA4130PK100-SIM
M12 flat washer Form C marine grade 316 BS 4320
BS 4320 Form C flat washer M12 A4 marine grade stainless steel, side profile
Flat washer face-on - M12 A4 stainless Form C BS 4320
Simfix product label - 125CA4130PK25-SIM
Simfix product label - 125CA4130PK100-SIM

Simfix

Flat Washer, Form C BS4320-C A4 A4 Stainless Steel (M12)

SKU 125CA4130PK25-SIM
£3.60
Pack size:
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M12 flat washer (Form C, large OD) in A4 stainless steel (316 marine grade) to BS4320-C. The large outer diameter spreads load over a wider area than a standard Form A washer - useful for oversized holes and soft parent materials. A4 (316) resists saltwater and chloride attack for coastal and marine use. Free next-day UK delivery on orders over £50.
£3.60
M12 flat washer Form C marine grade 316 BS 4320 BS 4320 Form C flat washer M12 A4 marine grade stainless steel, side profile Flat washer face-on - M12 A4 stainless Form C BS 4320 Simfix product label - 125CA4130PK25-SIM Simfix product label - 125CA4130PK100-SIM
M12 flat washer Form C marine grade 316 BS 4320 BS 4320 Form C flat washer M12 A4 marine grade stainless steel, side profile Flat washer face-on - M12 A4 stainless Form C BS 4320 Simfix product label - 125CA4130PK25-SIM Simfix product label - 125CA4130PK100-SIM

This M12 Form C flat washer is manufactured to BS4320-C in A4 stainless steel (316 marine grade). BS4320 Form C specifies a large outer diameter washer, providing a significantly wider bearing surface than a standard DIN 125-A Form A washer for the same bolt size. A4 (316) grade gives superior resistance to chloride and saltwater attack compared with A2 (304), making this the correct choice for coastal, marine, pool, and chemical environments where load distribution and corrosion resistance are both critical.

Typical applications

  • Marine and coastal installations - boat fittings, pier fixings, jetty hardware
  • Swimming pool surrounds, water treatment plant, and pump assemblies
  • Timber decking and fencing in wet or coastal conditions
  • Chemical plant, food processing, and washdown environments

Available in packs of 25 to 100, with free next-day UK delivery on orders over £50 and 30-day no-quibble returns.

Fastener styleForm C flat washer
StandardBS4320-C
MaterialA4 stainless steel (316)
Property classA4-50/70
Thread sizeM12
Head typeN/A
Surface finishPlain (no plating)
HS commodity code7318220091
Recommended useMarine

RoHS and REACH compliant.

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