1/4 in x 4-1/2 in Carriage Bolt Kit (100 Pack) - Hot Dip Galvanized

Our review of this 1/4 in x 4-1/2 in carriage bolt kit finds it best suited for homeowners and builders who need a reliable, long-lasting fastener for exterior projects. The biggest reason to buy is the hot dip galvanized coating coupled with full accessory counts: 100 Grade 307A carriage bolts, 100 USS flat washers and 100 1/4 in-20 hex nuts, which collectively simplify large deck, pergola or gazebo builds and repairs. The review focuses on real-world fit, corrosion resistance and the semi-flush flat head that keeps finished surfaces neat.

Key Features

• Complete kit: Comes with 100 carriage bolts, 100 USS flat washers and 100 hex nuts so a single purchase covers large projects without repeated orders.
• Hot dip galvanized: The heavy zinc coating provides superior corrosion resistance for exterior use, including contact with treated lumber.
• Semi-flush flat head: The flat head yields a semi-flush finish that works well for decks, pergolas and visible structural connections.
• Built to standards: Meets or exceeds common industry specifications, which helps ensure dimensional consistency and interchangeability.
• Practical dimensions: 1/4 in diameter with a 4-1/2 in length and a 0.578 in head diameter for solid holding in medium-thickness timbers.

Who It's For

This kit is ideal for DIY homeowners, landscape builders and contractors who need a bulk supply of consistent carriage bolts for outdoor projects. The inclusion of USS thick washers and Grade 2/A nuts means installers can assemble and tighten connections on-site without hunting for compatible fasteners.

Those who should look elsewhere include people who need stainless steel for marine environments or specialty head styles beyond the flat carriage head; this kit is specifically hot dip galvanized and focused on traditional semi-flush applications.

Pros & Cons

Pros

• Complete 100-piece kit reduces trips to the hardware store and speeds installation for large projects.
• Hot dip galvanized coating offers strong corrosion resistance for outdoor and treated lumber use.
• Flat head creates a neat, semi-flush finish that suits visible deck and pergola hardware.
• Conforms to industry standards so parts are predictable and compatible.

Cons

• Not stainless steel, so those with near-shore or highly corrosive exposures may prefer a different material.
• Fixed length and head style limit use where a shorter bolt or different head is required.

Specifications

Diameter	1/4 in
Length	4-1/2 in
Head diameter	0.578 in
Nut size	1/4 in-20, wrench 7/16 in
Washer outside diameter	47/64 in
Contents	100 carriage bolts, 100 USS flat washers, 100 Grade 2/A hex nuts
Coating	Hot dip galvanized for exterior use

Our Verdict

For anyone building or repairing decks, pergolas or other outdoor structures who wants a bulk, ready-to-use fastener set, this 100-piece carriage bolt kit offers reliable corrosion protection and a tidy semi-flush finish. It delivers strong value through complete accessory counts and standards compliance, though buyers needing stainless steel should select a different material.

Frequently Asked Questions

Are these bolts suitable for pressure-treated lumber?
Yes; the hot dip galvanized coating is specified as suitable for use in ACQ treated lumber and similar exterior applications.

Do the nuts match standard wrench sizes?
The hex nuts are 1/4 in-20 and use a 7/16 in wrench, which is common and easy to find in hand tool sets.

Will the flat head sit flush with wood surfaces?
The flat head provides a semi-flush finish; it is designed to sit neat against wood but may not be fully countersunk without additional routing.