Collection: Metric 316/A4 Socket Cap Screws
Marine grade metric socket cap screws in 316 (A4) stainless steel, from M3 to M12. Choose socket head (DIN 912), button head (ISO 7380), or flat head countersunk (DIN 7991). Every piece is genuine 316, never A2 or 18-8. Orders ship same or next business day.
Which head style do you need?
| Style |
Standard |
Best for |
| Socket head |
DIN 912 / ISO 4762 |
Highest strength, tight clearances, engine and mechanical work |
| Button head |
ISO 7380 |
Low, rounded profile for trim, panels, and exposed hardware |
| Flat head |
DIN 7991 |
Flush, countersunk installs on deck hardware and hatches |
Hex key sizes
| Thread |
Pitch |
Socket head key |
Button / flat head key |
| M3 |
0.5 |
2.5 mm |
2 mm |
| M4 |
0.7 |
3 mm |
2.5 mm |
| M5 |
0.8 |
4 mm |
3 mm |
| M6 |
1.0 |
5 mm |
4 mm |
| M8 |
1.25 |
6 mm |
5 mm |
| M10 |
1.5 |
8 mm |
6 mm |
| M12 |
1.75 |
10 mm |
8 mm |
Why A4 and not A2?
A2 (304) stainless is fine on land. In salt water it pits and tea-stains. A4 (316) adds molybdenum, which gives it far better resistance to chloride corrosion. That's why it's the standard for boats, docks, and anything near the coast. Our socket cap screws are property class [A4-70 / A4-80], fully passivated.
How to measure a metric socket cap screw
Measure thread diameter in millimeters (an M6 screw is 6 mm across the threads). For socket head and button head screws, measure length from under the head to the tip. For flat head screws, measure overall length, head included. Pitch is the distance between threads; all of our metric screws are standard coarse thread.
Who uses metric 316 socket cap screws?
If your boat was built in Europe (Beneteau, Jeanneau, Bavaria, Hallberg-Rassy, and many others), most of its deck hardware and fittings are metric. So are most marine engines and outboards. Replacing those fasteners with imperial sizes means re-tapping holes, so match what's there with true metric A4.
