3/8 x 3-1/2 Lag Screw Kit (50 Pack) - Weatherproof Industrial Grade

In this review of the 3/8 x 3-1/2 Lag Screw Kit, the bottom line is simple: this kit is for contractors, cabinet installers, deck builders and serious DIYers who need a reliable, weatherproof fastener in production quantities. The reviewer finds the combination of Grade A307 lag bolts and USS flat washers, supplied as a 50 screw and 50 washer kit, delivers consistent strength and value. The single biggest reason to buy is the four-layer Black Ruspert ceramic coating, which provides improved rust resistance for exterior use and compatibility with ACQ treated lumber.

Key Features

• Size and fit: Each lag screw is 3/8 in diameter and 3-1/2 in long, providing deep embedment for structural connections.
• Complete kit: The package includes 50 Grade 307A hex lag screws and 50 USS flat washers, so projects that require matched hardware are ready out of the box.
• Weatherproof coating: Black Ruspert ceramic coating offers a multi-layer barrier that improves corrosion resistance for exterior applications.
• Code conformity: Meets common industry standards for hardware strength and dimensions, making them suitable for many commercial and industrial uses.
• Lumber compatibility: Rated for use with ACQ treated lumber when installed properly, expanding their use on outdoor builds.

Who It's For

This kit is best for professionals and experienced DIYers who install multiple lag connections and want consistent hardware in quantity. Contractors who mount heavy millwork, signage, outdoor displays or ledger boards will appreciate the included washers and the industrial grade of the bolts.

It is not aimed at casual one-off users who need a single bolt or a decorative fastener; those users should look for smaller multi-size assortments or stainless options if finish longevity under harsh coastal exposure is a top priority.

Pros & Cons

Pros

• Durable Grade A307 construction provides the strength expected for structural lag applications.
• The 50 screw and 50 washer count simplifies large jobs and reduces repeat ordering.
• Black Ruspert coating delivers better rust resistance than standard galvanized finishes for outdoor use.
• Washers included help distribute load and protect wood surfaces during tightening.

Cons

• The coated finish can chip or flake during heavy impact driver installation, so care or pilot holes are recommended.
• Not stainless steel, so extreme marine environments may require a different alloy.

Specifications

Diameter	3/8 in
Length	3-1/2 in
Head width	9/16 in
Kit contents	50 lag screws and 50 USS flat washers (total 100 pcs)
Washer outside diameter	1 in
Coating	Black Ruspert 4-layer ceramic coating
Standards	Meets ASTM A307 and ASME B18.2.1

Our Verdict

The 3/8 x 3-1/2 Lag Screw Kit is a practical choice for builders who need a reliable, weather-resistant fastener in bulk. It balances strength, value and improved rust resistance, making it a sensible buy for outdoor projects and commercial installations, provided installers use pilot holes or moderate torque to protect the coating.

Frequently Asked Questions

Are these lag screws suitable for treated lumber?
Yes, the product is specified as suitable for use with ACQ treated lumber when installed correctly.

Do the screws come with washers?
Yes, the kit includes 50 USS flat washers sized 1 in outside diameter to accompany the 50 lag screws.

Should I predrill before installing?
Yes, a pilot hole is recommended to ease installation and reduce the risk of coating chipping or wood splitting.