A4 316 Marine Stainless Steel Flat Washers DIN 125, M1.6-M30

Overview

Engineered for the most demanding environments, these Form A flat washers in 18 sizes from M1.6 to M30 are made from A4 (316) marine grade stainless steel: DIN 125 Form A, similar to ISO 7089. They are the natural choice wherever a bolted joint has to shrug off saltwater, de-icing salt, washdown chemicals or sustained damp, without staining, pitting or rust bleed. Your finished work stays clean, and so does your reputation for a job done properly.

A4 (316) is a molybdenum-alloyed stainless steel. The molybdenum is what sets A4 apart from standard A2 stainless: it improves resistance to pitting and crevice corrosion caused by chlorides, which is why A4 is widely specified as "marine grade" for coastal, washdown and chemical-exposure applications. Each washer has a plain, unplated natural finish – stainless steel needs no surface coating to resist corrosion, so there is no plating to wear, flake or scratch through in service.

These are DIN 125 Form A washers, similar to ISO 7089: plain flat washers without a chamfer. Form A washers have a plain square edge on both faces (as opposed to the chamfered edge of Form B / ISO 7090), so they can be fitted either way up and seat flush against the mating surface.

This listing covers 18 sizes from M1.6 up to M30, as single washers or larger packs, so you can order the quantity the job needs.

Key Features

A4 (316) marine grade stainless steel – molybdenum-alloyed for genuine resistance to saltwater, chlorides and chemical exposure.
DIN 125 Form A, similar to ISO 7089 – square-edged (non-chamfered) profile for flush, either-way-up fitting.
Plain natural finish – no plating to wear through; the corrosion resistance is inherent to the material, not a coating.
18 sizes, M1.6 to M30 – covering everything from precision electronics fixings up to heavy structural bolts.
Single washers or larger packs – order the quantity you need for the job in hand.
Hardness HV 140 – from the product data sheet, with inside diameter, outside diameter and thickness listed for every size below.

Technical Specification

Dimensions below are from the product data sheet for every size in this listing. Metric figures are the governing dimension; imperial equivalents are shown for reference.

Thread Size (M)	Inside Ø d1	Outside Ø d2	Thickness h
M1.6	1.7 mm (0.067")	4.0 mm (0.157")	0.3 mm (0.012")
M2	2.2 mm (0.087")	5.0 mm (0.197")	0.3 mm (0.012")
M3	3.2 mm (0.126")	7.0 mm (0.276")	0.5 mm (0.020")
M4	4.3 mm (0.169")	9.0 mm (0.354")	0.8 mm (0.031")
M5	5.3 mm (0.209")	10.0 mm (0.394")	1.0 mm (0.039")
M6	6.4 mm (0.252")	12.0 mm (0.472")	1.6 mm (0.063")
M7	7.4 mm (0.291")	14.0 mm (0.551")	1.6 mm (0.063")
M8	8.4 mm (0.331")	16.0 mm (0.630")	1.6 mm (0.063")
M10	10.5 mm (0.413")	20.0 mm (0.787")	2.0 mm (0.079")
M12	13.0 mm (0.512")	24.0 mm (0.945")	2.5 mm (0.098")
M14	15.0 mm (0.591")	28.0 mm (1.102")	2.5 mm (0.098")
M16	17.0 mm (0.669")	30.0 mm (1.181")	3.0 mm (0.118")
M18	19.0 mm (0.748")	34.0 mm (1.339")	3.0 mm (0.118")
M20	21.0 mm (0.827")	37.0 mm (1.457")	3.0 mm (0.118")
M22	23.0 mm (0.906")	39.0 mm (1.535")	3.0 mm (0.118")
M24	25.0 mm (0.984")	44.0 mm (1.732")	4.0 mm (0.157")
M27	28.0 mm (1.102")	50.0 mm (1.969")	4.0 mm (0.157")
M30	31.0 mm (1.220")	56.0 mm (2.205")	4.0 mm (0.157")

Material	A4 (316) Stainless Steel
Hardness	HV 140
Standard	DIN 125 Form A, similar to ISO 7089
Edge Profile	Square edge, no chamfer (Form A)
Finish	Plain, natural (unplated)
Sizes	M1.6, M2, M3, M4, M5, M6, M7, M8, M10, M12, M14, M16, M18, M20, M22, M24, M27, M30

Typical Applications

Marine & coastal: boat fittings, deck hardware, pontoons, jetties and any assembly regularly exposed to salt spray or immersion.
Outdoor & infrastructure: railings, signage, fencing and structures exposed to de-icing salt or year-round weathering.
Industrial & chemical processing: plant and equipment exposed to washdown chemicals and process fluids.
General engineering & DIY: anywhere a non-corroding, non-staining washer is preferred over standard zinc-plated steel.

Fitting & Installation Guidance

Match the washer's thread size to the bolt, screw or stud diameter (e.g. an M8 bolt takes an M8 washer) – the bore is sized with clearance so the fastener passes through freely.
Fit the washer beneath the bolt head and/or nut to spread the clamping load over a wider area, reducing surface damage and the risk of the fastener pulling through soft or brittle materials.
Form A washers have no chamfer, so either face can be presented to the joint.
Where vibration is expected, pair with a suitable lock or spring washer in addition to this flat washer.

Common Questions

Which size do I need?
Match the washer to the bolt, screw or stud: an M8 bolt takes an M8 washer. The inside diameter, outside diameter and thickness of every size are in the table above.

Which way up does it fit?
Either way. Form A washers have no chamfer, so both faces sit flush against the joint.

What makes A4 (316) marine grade?
A4 is a molybdenum-alloyed stainless steel. The molybdenum improves resistance to pitting and crevice corrosion caused by chlorides, such as salt spray and de-icing salt.

Is there a coating that can wear off?
No. The washers are plain, natural stainless steel, so there is no plating to wear, flake or scratch through in service.

Specifications

Material	A4 Stainless Steel
Finish	plain finish (natural)
Size	M1.6 to M30 (18 sizes)
Weight	0.0006 kg

All 126 options and prices

Size	Pack Quantity	Price inc. VAT	ex. VAT	Per piece	Select
M1.6	1	£4.38	£3.65	-	Sold out
M1.6	10	£4.68	£3.90	£0.47	Sold out
M1.6	100	£5.38	£4.48	£0.05	Sold out
M1.6	20	£4.78	£3.98	£0.24	Sold out
M1.6	200	£6.78	£5.65	£0.03	Sold out
M1.6	3	£4.68	£3.90	£1.56	Sold out
M1.6	50	£4.98	£4.15	£0.10	Sold out
M10	1	£4.38	£3.65	-
M10	10	£4.98	£4.15	£0.50
M10	100	£8.68	£7.23	£0.09
M10	20	£5.28	£4.40	£0.26
M10	200	£12.78	£10.65	£0.06
M10	3	£4.78	£3.98	£1.59
M10	50	£6.98	£5.81	£0.14
M12	1	£4.38	£3.65	-
M12	10	£5.18	£4.31	£0.52	Sold out
M12	100	£10.48	£8.73	£0.10	Sold out
M12	20	£6.38	£5.31	£0.32	Sold out
M12	200	£17.78	£14.81	£0.09	Sold out
M12	3	£4.78	£3.98	£1.59
M12	50	£7.88	£6.57	£0.16	Sold out
M14	1	£4.48	£3.73	-
M14	10	£5.38	£4.48	£0.54
M14	100	£14.98	£12.48	£0.15
M14	20	£6.88	£5.73	£0.34
M14	200	£22.38	£18.65	£0.11	Sold out
M14	3	£4.88	£4.07	£1.63
M14	50	£8.98	£7.48	£0.18
M16	1	£4.48	£3.73	-
M16	10	£6.28	£5.23	£0.63	Sold out
M16	100	£16.48	£13.73	£0.16	Sold out
M16	20	£7.18	£5.98	£0.36	Sold out
M16	200	£25.18	£20.98	£0.13	Sold out
M16	3	£4.88	£4.07	£1.63
M16	50	£9.78	£8.15	£0.20	Sold out
M18	1	£4.48	£3.73	-	Sold out
M18	10	£6.68	£5.57	£0.67	Sold out
M18	100	£20.78	£17.31	£0.21	Sold out
M18	20	£7.98	£6.65	£0.40	Sold out
M18	200	£33.88	£28.23	£0.17	Sold out
M18	3	£4.98	£4.15	£1.66	Sold out
M18	50	£12.68	£10.57	£0.25	Sold out
M2	1	£4.38	£3.65	-
M2	10	£4.68	£3.90	£0.47
M2	100	£5.38	£4.48	£0.05
M2	20	£4.78	£3.98	£0.24
M2	200	£6.78	£5.65	£0.03
M2	3	£4.68	£3.90	£1.56
M2	50	£4.98	£4.15	£0.10
M20	1	£4.48	£3.73	-	Sold out
M20	10	£6.78	£5.65	£0.68	Sold out
M20	100	£21.28	£17.73	£0.21	Sold out
M20	20	£7.98	£6.65	£0.40	Sold out
M20	200	£34.88	£29.07	£0.17	Sold out
M20	3	£4.98	£4.15	£1.66	Sold out
M20	50	£14.48	£12.07	£0.29	Sold out
M22	1	£4.58	£3.81	-	Sold out
M22	10	£7.18	£5.98	£0.72	Sold out
M22	100	£25.98	£21.65	£0.26	Sold out
M22	20	£8.98	£7.48	£0.45	Sold out
M22	200	£44.28	£36.90	£0.22	Sold out
M22	3	£5.18	£4.31	£1.73	Sold out
M22	50	£16.88	£14.07	£0.34	Sold out
M24	1	£4.58	£3.81	-	Sold out
M24	10	£7.88	£6.57	£0.79	Sold out
M24	100	£32.28	£26.90	£0.32	Sold out
M24	20	£10.28	£8.57	£0.51	Sold out
M24	200	£56.88	£47.40	£0.28	Sold out
M24	3	£5.38	£4.48	£1.79	Sold out
M24	50	£19.98	£16.65	£0.40	Sold out
M27	1	£4.68	£3.90	-	Sold out
M27	10	£8.68	£7.23	£0.87	Sold out
M27	100	£39.98	£33.31	£0.40	Sold out
M27	20	£14.18	£11.81	£0.71	Sold out
M27	200	£72.48	£60.40	£0.36	Sold out
M27	3	£6.38	£5.31	£2.13	Sold out
M27	50	£23.88	£19.90	£0.48	Sold out
M3	1	£4.38	£3.65	-
M3	10	£4.68	£3.90	£0.47
M3	100	£4.88	£4.07	£0.05	Sold out
M3	20	£4.68	£3.90	£0.23	Sold out
M3	200	£4.98	£4.15	£0.02	Sold out
M3	3	£4.68	£3.90	£1.56
M3	50	£4.78	£3.98	£0.10	Sold out
M30	1	£4.78	£3.98	-	Sold out
M30	10	£9.58	£7.98	£0.96	Sold out
M30	100	£49.18	£40.98	£0.49	Sold out
M30	20	£15.98	£13.31	£0.80	Sold out
M30	200	£90.68	£75.57	£0.45	Sold out
M30	3	£6.68	£5.57	£2.23	Sold out
M30	50	£28.48	£23.73	£0.57	Sold out
M4	1	£4.38	£3.65	-
M4	10	£4.68	£3.90	£0.47
M4	100	£5.78	£4.81	£0.06
M4	20	£4.68	£3.90	£0.23
M4	200	£7.68	£6.40	£0.04
M4	3	£4.68	£3.90	£1.56
M4	50	£5.58	£4.65	£0.11
M5	1	£4.38	£3.65	-
M5	10	£4.68	£3.90	£0.47
M5	100	£5.88	£4.90	£0.06
M5	20	£5.48	£4.57	£0.27
M5	200	£7.88	£6.57	£0.04
M5	3	£4.68	£3.90	£1.56
M5	50	£5.58	£4.65	£0.11
M6	1	£4.38	£3.65	-
M6	10	£4.68	£3.90	£0.47
M6	100	£7.88	£6.57	£0.08
M6	20	£5.58	£4.65	£0.28
M6	200	£8.68	£7.23	£0.04
M6	3	£4.68	£3.90	£1.56
M6	50	£5.78	£4.81	£0.12
M7	1	£4.38	£3.65	-	Sold out
M7	10	£5.58	£4.65	£0.56	Sold out
M7	100	£8.98	£7.48	£0.09	Sold out
M7	20	£5.78	£4.81	£0.29	Sold out
M7	200	£10.98	£9.15	£0.05	Sold out
M7	3	£4.68	£3.90	£1.56	Sold out
M7	50	£6.38	£5.31	£0.13	Sold out
M8	1	£4.38	£3.65	-
M8	10	£5.18	£4.31	£0.52
M8	100	£8.48	£7.07	£0.08
M8	20	£5.68	£4.73	£0.28
M8	200	£9.88	£8.23	£0.05	Sold out
M8	3	£4.38	£3.65	£1.46
M8	50	£5.98	£4.99	£0.12