3/8 in x 8 in Black Carriage Bolt Kit - Ceramic Coated for Exterior

Our review of this 3/8 in x 8 in carriage bolt kit finds it best suited for outdoor projects where corrosion resistance and a semi-flush finish matter. The kit includes 25 Grade 307A carriage bolts, USS flat washers, and grade 2 hex nuts, all finished with a 5-layer ceramic black ruspert coating that claims roughly twice the rust protection of standard galvanized hardware. For builders fitting decks, pergolas, gazebos or bolting structural elements of small dwellings, the combination of length, head size and corrosion-focused finish is the single biggest reason to consider this kit.

Key Features

• Complete 25-piece kit: Comes with 25 carriage bolts, 25 USS thick washers and 25 hex nuts so a typical small decking or pavilion run can be fitted without sourcing extra fasteners.
• 5-layer ceramic black ruspert coating: Provides enhanced rust resistance for exterior use and improves appearance on visible outdoor structures.
• Grade 307A bolts: The specified bolt grade gives reliable shear and tensile performance for many heavy duty outdoor applications.
• Semi-flush flat head: The carriage bolt head diameter and flat profile deliver a restrained, semi-flush finish ideal for decks, pergolas and gazebos.
• Standard hardware sizes: 3/8 in diameter and 8 in length with a 9/16 in nut wrench size makes these easy to install with common tools.
• Washer and nut match: USS thick washers and grade 2 hex nuts are included to distribute load and secure the connection without extra purchases.

Who It's For

This kit is for DIYers and contractors installing outdoor structures like decks, pergolas, gazebos or small cabins who want a consistent, black finish and improved corrosion resistance over plain galvanized fasteners. The 8 in length and 3/8 in diameter suit through-bolting tasks where a carriage head and washer are required for a neat, semi-flush look.

Those who need specialty high-strength fasteners or stainless steel for extreme coastal corrosion should look elsewhere; if maximum marine-grade corrosion resistance is required, stainless options are preferable. Also, projects needing metric sizes or lengths other than 8 in will need different kits.

Pros & Cons

Pros

• Good value: a full set of bolts, washers and nuts reduces the need to buy components separately.
• Better rust protection: the five-layer ceramic black ruspert finish offers improved outdoor durability compared with standard galvanized finishes.
• Clean look: semi-flush flat head and black coating provide an attractive finished appearance on visible structures.

Cons

• Rust resistance mixed in practice: some customers reported variable long-term rust performance depending on exposure conditions.
• Not stainless: for extreme marine environments, this coated carbon option is less durable than stainless steel.

Specifications

Diameter	3/8 in
Length	8 in
Head diameter	0.813 in
Nut wrench size	9/16 in
Washer outside diameter	1 in (USS thick)
Kit contents	25 carriage bolts, 25 USS flat washers, 25 grade 2 hex nuts
Coating	5-layer ceramic black ruspert

Our Verdict

The 3/8 in x 8 in carriage bolt kit is a practical, cost-effective choice for outdoor builds that need a clean, semi-flush finish and better-than-galvanized corrosion protection. It is especially good for decks, pergolas and gazebos where appearance and a complete matched kit matter; choose stainless if you need marine-grade durability.

Frequently Asked Questions

Are these bolts suitable for exterior use?
Yes, they are coated with a 5-layer ceramic black ruspert finish designed to improve rust resistance for exterior applications.

What tools are needed to install them?
A 9/16 in wrench or socket for the hex nut and standard drill or holesaw to accommodate a 3/8 in bolt will be sufficient.

Do the kits include washers and nuts?
Yes, each kit includes 25 USS thick washers and 25 grade 2 hex nuts matched to the carriage bolts.