Special Offers
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6.3 X 25 Hex Head Self Drilling Screw DIN 7504-K A2 Stainless Steel
In stockRRP From £11.21 -
M8 Flat Washer, Form A DIN 125-A A2 Stainless Steel
In stockRRP From £2.69 -
M8 Nylon Insert Nut DIN 985 A2 Stainless Steel
In stockRRP From £3.23 -
M10 Hexagon Full Nut DIN 934 A2 Stainless Steel
In stockRRP From £3.99
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M8 X 110 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M8 x 110mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £10.90RRP From £10.90 -
M8 X 100 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M8 x 100mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £14.04RRP From £14.04 -
M6 X 70 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 70mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £3.78RRP From £3.78 -
M6 X 70 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 70mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £8.97RRP From £8.97 -
M6 X 90 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 90mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £4.16RRP From £4.16 -
M6 X 65 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 65mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £4.77RRP From £4.77 -
M6 X 60 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 60mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £8.51RRP From £8.51 -
M6 X 50 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 50mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £8.23RRP From £8.23 -
M6 X 55 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 55mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £3.07RRP From £3.07 -
M6 X 45 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 45mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £8.19RRP From £8.19 -
M6 X 35 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 35mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £7.58RRP From £7.58 -
M6 X 45 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 45mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £4.34RRP From £4.34 -
M6 X 30 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 30mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £3.48RRP From £3.48 -
M6 X 35 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 35mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £3.62RRP From £3.62 -
M6 X 40 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 40mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £8.15RRP From £8.15 -
M6 X 20 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 20mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £3.05RRP From £3.05 -
M6 X 25 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 25mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £4.47RRP From £4.47 -
M6 X 30 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 30mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £7.02RRP From £7.02 -
M6 X 25 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 25mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £2.37RRP From £2.37 -
M6 X 150 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 150mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £4.53RRP From £4.53 -
M6 X 20 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 20mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £3.34RRP From £3.34 -
M6 X 140 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 140mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £6.48RRP From £6.48 -
M6 X 16 Cup Square Bolt DIN 603 A2 Stainless Steel
In stockThis M6 x 16mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A2 stainless steel (304 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £2.29RRP From £2.29 -
M6 X 16 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 16mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £6.34RRP From £6.34 -
M6 X 120 Cup Square Bolt DIN 603 A4 Stainless Steel
In stockThis M6 x 120mm coach bolt (cup square head bolt) is manufactured to DIN 603 in A4 stainless steel (316 grade). DIN 603 specifies a domed round head with a small square neck directly below the...RRP From £9.22RRP From £9.22
A cup square bolt, also called a carriage bolt or coach bolt, has a rounded head and a square shoulder underneath that pulls into timber and stops the bolt turning while you tighten the nut. Simfix stocks them to DIN 603 in A2 (304) and A4 (316), from M5 to M16 and from 12mm to 300mm long, depending on diameter.
Used for fencing, decking, gates, pergolas and post supports. Choose A2 for inland outdoor work and A4 near the coast or where timber stays wet.
Frequently asked questions
What is a cup square bolt?
A cup square bolt has a rounded (cup) head and a square section directly under it. The square shoulder pulls into timber as you tighten the nut, stopping the bolt from spinning. It is also called a carriage bolt or coach bolt. Simfix stocks cup square bolts to DIN 603 in A2 (304) and A4 (316), M5 to M16.
Carriage bolt vs coach bolt vs coach screw: what's the difference?
Carriage bolt and coach bolt are two UK names for the same fastener, called a cup square bolt at Simfix (DIN 603): a bolt with a rounded head, tightened with a nut. A coach screw has a hex head and a wood screw thread instead of a nut, and is driven with a spanner into a pre-drilled hole, to DIN 571.
Are cup square bolts available in A4 (316)?
Yes. Simfix stocks DIN 603 cup square bolts in A4 (316) from M5 to M16, as well as in A2 (304). Choose A4 for coastal or salt-exposed timber and for timber that stays wet; A2 suits fencing, decking and gates away from the coast.
What sizes of cup square bolt does Simfix stock?
M5, M6, M8, M10, M12 and M16 diameters in both A2 (304) and A4 (316), in lengths from 12mm to 300mm depending on diameter. Each product listing is a single diameter and length, and not every length is stocked at every size and grade.
Sizes, grades and pack quantities vary by product type. Check the individual product listing for the exact specification and current availability.