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ARP 661-1003 Metric Hex Bolt Kit M6 Stainless Steel 5-Pack

Manufacturer

ARP

<h3>The Gold Standard in Performance Fasteners</h3> <p>When racing enthusiast Gary Holzapfel recognized that fastener failure was causing many engine breakdowns in 1968, he founded Automotive Racing Products (ARP) to solve a critical problem in motorsports. Drawing on his aerospace fastener manufacturing experience, Holzapfel created a company that would revolutionize the performance fastener industry. Today, ARP stands as the world's premier manufacturer of high-strength bolts, studs, nuts, and specialized hardware for racing and high-performance applications.</p> <p>ARP controls all aspects of the manufacturing process in-house, with all operations closely monitored, enabling the company to maintain its reputation for zero-defect quality. Every fastener undergoes forging, heat treatment, thread rolling, and precision finishing at ARP's Southern California facilities, which span over 115,000 square feet. This vertically integrated approach ensures that each component meets exacting standards for strength, fatigue resistance, and reliability under extreme conditions.</p> <h3>Engineered for Championship Performance</h3> <p>ARP's customer roster reads like a who's who of professional motorsports. The product line ranges from quality high-performance OEM replacement parts to exotic specialty hardware for Formula 1, IndyCar, NASCAR and NHRA drag racing and marine applications. The company's fasteners have secured victories in virtually every major racing championship worldwide, from Top Fuel dragsters to Formula One cars, proving their worth under the most demanding conditions imaginable.</p> <p>The brand's <a href="/48-arp-engine-cylinder-head-bolt-set-10306">engine cylinder head bolt sets</a> represent the cornerstone of ARP's catalog, offering engine builders the clamping force and reliability needed to prevent head gasket failure in high-boost and high-compression applications. These precision-engineered fasteners utilize proprietary materials and heat treatments that deliver up to ten times the fatigue strength of conventional bolts, making them essential for any serious performance build.</p> <p>For engine internals, ARP manufactures <a href="/48-arp-engine-connecting-rod-5276">connecting rods</a> designed to withstand extreme cylinder pressures and high RPM loads. Each rod is manufactured to aerospace standards with tight tolerances and superior material properties. Whether you're building a street performance engine or a full competition powerplant, ARP connecting rods provide the strength and consistency that professional engine builders demand.</p> <h3>Complete Fastener Solutions</h3> <p>Beyond engine components, ARP's product range extends throughout the entire vehicle. The company's <a href="/48-arp-wheel-lug-stud-7680">wheel lug studs</a> offer critical safety and performance benefits for racing and high-performance street applications, providing greater clamping force and durability than factory studs. ARP's product line contains thousands of part numbers and has expanded to include virtually every fastener found in an engine and driveline.</p> <p>Individual <a href="/48-arp-engine-cylinder-head-bolt-5308">engine cylinder head bolts</a> are also available for custom applications or specific replacement needs, manufactured to the same exacting standards as complete sets. This flexibility allows builders to source exactly what they need for specialized builds or repairs without compromising on quality.</p> <p>What sets ARP apart is not just the breadth of their catalog, but their willingness to develop custom solutions for unique applications. The company maintains complete R&D capabilities, including metallurgical research, product design, prototype machining, and extensive laboratory testing. This engineering expertise ensures that whether you're installing a simple head stud kit or building a record-setting race engine, ARP fasteners deliver the reliability and performance that professionals trust.</p>

Part Number

661-1003
07/12/2036 12:08 PM
Sale Price

$12.77

4 left at this price

delivery box

Usually delivered within 2 days

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No Hassle Returns

No Hassle Returns

Live-in-stock inventory

Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The ARP 661-1003 is a premium 5-piece metric hex bolt kit designed for differential and ring & pinion installations, as well as general automotive, marine, and trailer applications. These high-quality fasteners are manufactured from specially alloyed ARP 300 stainless steel, providing exceptional strength and corrosion resistance.

Key Features:

  • Nominally rated at 180,000 psi tensile strength for superior clamping force
  • Constructed from ARP 300 stainless steel for rust-free, maintenance-free performance
  • Premium polished finish for professional appearance
  • Substantially stronger than standard Grade 8 hardware
  • 12-point head design for easier installation in tight spaces
  • Includes matching washers for complete installation

ARP fasteners are the choice of professional engine builders and performance enthusiasts who demand reliability and precision. Each bolt is manufactured to exacting tolerances and undergoes rigorous quality control to ensure consistent performance in critical fastening applications.

Products specifications

Fastener Finish

Black oxide

Fastener Head Style

Hex

Fastener Material

Chromemoly

Fastener Yield Strength (psi)

170,000 psi

Material

Black Oxide

Quantity

Sold as a set of 5.

Size

M8 x 1.25 x 30

Underhead Length (in)

1.181 in.

Underhead Length (mm)

30mm

Washers Included

Yes

Wrench Diameter

10mm

Wrenching

10mm

all good

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Good selection of auto parts, great parts, and really fast shipping. Honestly I don't understand why there are so many negative reviews for this company. I received no compensation for this review, will certainly use Autoplicity again.

No hassels... exact match to old worn tires.

thanks

I had to place my order 4 times to get the system to accept the quantity I needed. I also checked into your email to check on my order and was told that my order did not exist. I had to call to make sure it hadn't been lost. Love the shocks, just installed this morning.

Easy peasy It was quick Didn't have time to change my mind

Straight forward pricing and great product!!!

Arrived in good working order.

Easy transaction, great price.

Autoplicity gave quick shipping and great status notifications of my order. Products were as advertised. Best prices around. Would definately recommend this company to people.

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