Marine Grade Metric 316/A4 Stainless Steel Fasteners

If you’re working in a saltwater, coastal, or otherwise corrosive environment, fastener selection matters. Our inventory of Metric 316 stainless steel fasteners (A4 stainless) is curated specifically for marine use where corrosion resistance, consistent fit, and long-term reliability are critical. 316/A4 stainless offers substantially better resistance to corrosion than 304/A2 (18-8) stainless due to its alloy composition, making it the right choice for boats, docks, waterfront construction, and outdoor equipment exposed to moisture and chlorides. 

This page is your hub for our most commonly used metric stainless steel fastener types, including bolts, socket screws, nuts, and washers. Whether you’re doing a full refit, replacing deck hardware, or building corrosion-resistant assemblies, you’ll find true marine-grade fasteners here, not mystery alloy hardware.

What does A4 mean?

A4 stainless steel is the European designation commonly associated with 316 stainless steel, widely considered the standard “marine grade” stainless. It’s chosen because it holds up far better than A2/304 stainless when exposed to salt spray, seawater, and harsh marine conditions.

Choosing the right metric fastener type:

Not sure which category you need? Here’s a quick guide:

Metric Hex Bolts / Cap Screws (DIN 933) – Strong, widely used, easy to install with standard tools, ideal for mechanical and structural fastening.

Metric Socket Head Cap Screws (DIN 912) – High strength, clean look, excellent for tight clearances and precision assemblies.

Metric Button Head Socket Screws (ISO 7380) – Great when you want a low-profile rounded head four surface mounting with an Allen/socket drive. 

Metric Flat Head Socket Screws (DIN 7991) – Countersunk/flush finish for clean installs and reduced snag points with the convenience of and Allen/socket drive.

Metric Nuts – Essential for fastening metric sized bolts. Our 316/A4 Metric sized nuts are high quality, marine grade, and finely machined for that perfect fit.

Metric Washers– Load distribution, surface protection, and fastener locking, our 316/A4 metric flat washers, fender washers, and split lock washers will get the job done on your metric assemblies while being highly corrosion resistant.

Why buy metric 316 stainless fasteners from Fair Wind Fasteners?

We built Fair Wind Fasteners for people who don’t want to gamble on quality, especially on boats. Our metric stainless selection is designed for boat builders, refit yards, and serious DIY owners who want:

• Marine-grade corrosion resistance (316 / A4)
• Consistent sizing and thread fit
• Curated categories so you can find what you need fast
• The ability to order the right fasteners for the job, get them shipped fast, and have confidence is the quality of the fastener that is holding together your critical components.