ARP Stainless Steel 3/8-16 12-Point Bolts Pack of 5 — 170,000 PSI Tensile, Polished Finish

ARP 6131250 are polished stainless-steel 3/8-16, 12-point bolts sold in a convenient five-pack and engineered for high tensile strength and corrosion resistance.

These bolts combine a rustproof stainless alloy finish with a nominal tensile rating of 170,000 PSI, giving you a stronger, longer-lasting fastener than typical Grade 8 hardware. Intended for demanding automotive, marine, and trailer applications, each bolt has a compact 12-point head for tight-clearance wrenching and a standardized 3/8"-16 thread for broad compatibility. The under-head length measures 1.250" and wrenching size is 3/8", and they arrive packaged five to a card for organized storage and quick access.

How durable are these ARP stainless bolts compared with standard fasteners?

ARP 6131250 bolts are nominally rated at 170,000 PSI tensile strength, which places them well above common Grade 8 fasteners. The combination of high tensile capability and a proprietary Stainless 300 alloy enhances resistance to shear and stretch under load, while the polished finish reduces surface corrosion in humid or salty environments.

• 170,000 PSI nominal tensile rating for higher safety margin
• Stainless 300 alloy resists rust and environmental degradation
• Polished surface for long-term finish retention
• 12-point head reduces slippage in tight access areas

Will these bolts fit my project — what are the exact dimensions and thread details?

Each bolt is 3/8" in diameter with a standard 16 threads-per-inch (3/8-16) pitch, a 1.250" under-head length, and a 3/8" wrenching size. These are common dimensions used across many engine, chassis, and accessory mounting points, making them a straightforward replacement or upgrade for matched applications.

• Diameter: 3/8" (0.375")
• Thread pitch: 16 TPI (standard 3/8-16)
• Under-head length: 1.250" for typical clearance needs
• Wrenching size: 3/8" compatible with compact tools

How do the 12-point heads benefit installation and maintenance?

The compact 12-point head design lets you access fasteners in confined or awkward spaces where larger hex heads won't fit. It offers more contact points for a wrench, reducing the chance of rounding and enabling smaller incremental turns when aligning parts. That makes them especially useful in engine bays, turbo or manifold work, and tight trailer or marine fittings.

• 12-point geometry for increased wrenching contact
• Smaller head profile for tight-clearance applications
• Reduced risk of rounded corners during torqueing
• Easier alignment when working in cramped spaces

Are these bolts suitable for outdoor and marine environments?

Yes — the Stainless 300 proprietary alloy and polished finish are formulated to withstand moisture and salt exposure better than plain steel fasteners. While no fastener is truly maintenance-free in all extreme conditions, these bolts are engineered to maintain appearance and structural integrity in automotive, marine, and trailer settings with minimal upkeep.

• Polished stainless surface resists staining and pitting
• Suitable for humid and coastal installations with proper care
• Packaged in a five-count card to keep items organized
• Ideal when corrosion resistance and strength are priorities

Who is this for: ARP 6131250 3/8-16 12-point stainless bolts are intended for mechanics, performance builders, marine technicians, and DIY enthusiasts who need compact-head, high-strength fasteners that resist rust. Choose this five-pack when you want a reliable upgrade over standard Grade 8 bolts for engine components, exhaust or manifold attachments, trailer hardware, or other applications where tensile strength and corrosion resistance matter.