3/8 x 4 in Lag Screw Kit (50 Pack) - Galvanized Hardware for Outdoor

In this review the 3/8 x 4 in Lag Screw Kit (50 Pack) is evaluated for homeowners and pros who need a reliable supply of lag screws for deck building, fence posts, and general outdoor projects. The biggest reason to buy is the combination of quantity and corrosion protection: the kit includes 50 Grade 307A lag bolts with matching USS flat washers and a hot-dip galvanized finish that helps resist rust in exterior and ACQ-treated lumber applications. It is a practical choice when a large, consistent supply of 3/8 in by 4 in fasteners is required.

Key Features

• Diameter and length: The 3/8 in diameter and 4 in length suit common structural connections in wood where deep embedment is needed for good hold.
• Included washers: The kit contains 50 USS flat washers (1 in OD) to distribute load and reduce wood crushing under the head during tightening.
• Hot-dip galvanized: The heavy galvanizing offers superior rust resistance compared with plain steel, making these bolts suitable for outdoor and treated lumber use.
• Industrial standards: Conformance to ASTM A307, ASME B18.2.1, ASME B18.21.1, and ASTM F2329 ensures consistent dimensions and material expectations for commercial or DIY projects.
• Grade 307A fasteners: The Grade 307A specification provides predictable tensile properties for common structural connections when installed appropriately.

Who It's For

This kit is aimed at homeowners, contractors, and woodworkers who undertake medium to large outdoor projects such as decks, pergolas, fencing, and structural repairs where multiple identical lag screws are needed. The large quantity and included washers reduce trips to the hardware store and keep fasteners consistent across a job.

Those who should look elsewhere include users who require stainless steel fasteners for prolonged coastal exposure or who need specialty thread forms or lengths not offered in this 3/8 in by 4 in size. Also consider different grades if very high tensile strength beyond Grade 307A is required.

Pros & Cons

Pros

• Hot-dip galvanizing provides improved corrosion resistance for outdoor projects and ACQ-treated lumber.
• Large 50-count supply with matching 1 in OD USS washers offers good value for multi-screw jobs.
• Meets common ASTM and ASME dimensional and material standards for predictable performance.

Cons

• Some users report mixed hold capacity under extreme loads, so pilot holes and correct installation are important to avoid breakage.

Specifications

Diameter	3/8 in
Length	4 in
Head width	9/16 in
Kit contents	50 lag bolts and 50 USS flat washers
Washer outside diameter	1 in
Finish	Hot-dip galvanized
Standards	ASTM A307, ASME B18.2.1, ASME B18.21.1, ASTM F2329

Our Verdict

The 3/8 x 4 in Lag Screw Kit is a sensible, value-oriented choice for most outdoor woodworking and structural repair tasks where corrosion resistance and quantity matter. With Grade 307A hardware, hot-dip galvanizing, and included washers, it suits deck and fence work well; installers should use pilot holes and match fastener grade to required load to avoid issues. For general exterior projects this kit provides dependable components at a competitive price.

Frequently Asked Questions

Are these screws suitable for ACQ-treated lumber?
Yes, the hot-dip galvanized finish is specified as suitable for use in ACQ-treated lumber to resist accelerated corrosion from treatment chemicals.

Do the screws come with washers?
Yes, the kit includes 50 USS flat washers with a 1 in outside diameter matched to the bolts.

Is a pilot hole required?
A pilot hole is recommended to ease installation and reduce the risk of wood splitting or bolt breakage, especially in hardwoods.