Marine Fasteners RP-75 Hex Cap Screw 5/16-18 x 3/4in 316 Stainless Steel 25-Pack

The Marine Fasteners RP-75 is a 5/16-18 x 3/4-inch hex cap screw sold in a convenient 25-piece pack. Manufactured from 316 marine-grade stainless steel, these fasteners are engineered to withstand the demanding conditions of saltwater and marine environments, including boats, docks, coastal structures, and other applications where corrosion resistance is critical.

316 stainless steel contains 2–3% molybdenum, which enhances its passive layer and provides superior resistance to pitting and crevice corrosion caused by chloride ions in seawater — making it a significant step up from standard 304 (18-8) stainless steel in marine applications.

Key Features:

• Thread Size: 5/16-18 UNC (coarse thread)
• Length: 3/4 inch (measured from underside of head to tip)
• Material: 316 Marine-Grade Stainless Steel (A4)
• Head Style: Hex cap screw with washer-face bearing surface
• Pack Quantity: 25 pieces
• Dimensionally compliant with ASME B18.2.1 for consistent fit and tolerances
• Superior corrosion resistance over 304 stainless — ideal for saltwater, splash zones, and continuous marine exposure
• Non-magnetic austenitic alloy construction

These hex cap screws are well-suited for securing deck hardware, through-bolt assemblies, marine fittings, dock hardware, and other structural or trim applications aboard boats and in coastal environments. The 5/16-18 coarse thread engages quickly and holds securely in tapped holes or with a standard 5/16-18 nut. The 25-piece pack is ideal for project use or keeping as on-board spares.