3/8in x 3in (50 Pack) Galvanized Carriage Bolt Kit - Heavy Exterior

Our review of this 3/8in x 3in carriage bolt kit finds it best suited for homeowners and small contractors who need a reliable, corrosion-resistant fastener for outdoor timber work. The single biggest reason to buy is the hot dip galvanized coating combined with Grade 307A carriage bolts, which together offer durable protection against rust for decks, pergolas and fences. The kit format with 50 bolts, 50 USS thick washers and 50 hex nuts makes it easy to tackle multiple connections without hunting for individual parts.

Key Features

• Hot dip galvanized coating: Provides superior corrosion resistance for long-lasting outdoor use on decks, gazebos and pergolas.
• Complete 50-piece kit: Includes 50 carriage bolts, 50 USS thick washers and 50 hex nuts so a full project run can be completed without extra purchases.
• Grade 307A carriage bolts: Offer reliable strength for heavy duty applications where a semi-flush flat head finish is preferred.
• Standardized hardware sizes: 3/8in nut diameter and 9/16in nut wrench size make these bolts compatible with common hand tools for fast installation.
• Semi-flush flat head design: The flat head gives a cleaner, less protruding finish than typical carriage heads while still locking into timber.

Who It's For

This kit is ideal for DIY homeowners installing fence rails, decking boards, pergola timbers or gazebo frames who want corrosion resistance without sourcing parts separately. It also suits small contractors and builders who appreciate a ready supply of consistent, Grade 307A carriage bolts for exterior timber connections.

Those who should look elsewhere include projects requiring stainless steel fasteners for coastal saltwater exposure or applications demanding higher strength grades than 307A; for those, a different material or higher grade bolt specification would be more appropriate.

Pros & Cons

Pros

• High corrosion resistance from the hot dip galvanized finish, extending outdoor life.
• Complete kit format saves time by supplying bolts, USS thick washers and hex nuts together.
• Consistent sizing with 3/8in diameter and 3in length fits common timber joinery and uses standard 9/16in wrenches.

Cons

• Washers receive mixed feedback from customers, so some may prefer to substitute thicker or different washer styles for specific projects.
• Grade 307A and grade 2 nuts are suitable for most exterior tasks but are not intended for very high tensile structural uses.

Specifications

Diameter	3/8in
Length	3in
Head diameter	0.813in
Nut wrench size	9/16in
Washer outside diameter	1in
Kit contents	50 carriage bolts, 50 USS thick washers, 50 hex nuts
Finish and grade	Hot dip galvanized; Grade 307A bolts, grade 2 hex nuts

Our Verdict

This 3/8in x 3in carriage bolt kit is a practical, value-oriented choice for exterior timber projects where corrosion resistance and convenience matter. The hot dip galvanized coating and complete 50-piece pack make it a smart buy for homeowners and small contractors, though those needing stainless material or higher tensile grades should consider alternatives.

Frequently Asked Questions

Are these bolts suitable for deck framing?
Yes, the Grade 307A bolts with hot dip galvanized coating are suitable for typical deck, pergola and gazebo timber connections.

What wrench size fits the nuts?
The hex nuts use a 9/16in wrench size for tightening.

Does the kit include washers and nuts?
Yes, the kit includes 50 USS thick washers and 50 hex nuts matched to the 50 carriage bolts.