Square U Bolts 3/8 in x 3 in x 7 in 15-Pack - Heavy Duty Zinc Plated

In this review the Dunzy 15 pack of square U bolts is evaluated for DIYers and light industrial use; it stands out for delivering a large quantity of simple, heavy duty fasteners suitable for securing 3 x 3 in square tubing and similar shapes. The bottom line: this set is best for projects that need many matching U bolts-trailers, small fabrication tasks, or maintenance-because the carbon steel zinc plating offers practical rust resistance and each kit includes plates and nuts for immediate assembly.

Key Features

• Common Size: The 3/8 in diameter, 3 in width and 7 in length dimensions make these U bolts suitable for standard 3 x 3 in square tubes and predictable clamping fit.
• Sufficient Quantity: Fifteen U bolts with 15 frame plates and 30 nuts provide enough hardware for multiple installations or spare parts without extra trips to the store.
• Hard Material: Carbon steel construction with zinc plating gives these fasteners tangible strength and improved resistance to rust in wet environments.
• Wide Applications: They work across industry, manufacturing, maintenance and automotive uses, particularly for fastening tube, wood or trailer components.
• Installation Tip: The manufacturer recommends using lubricant and a manual wrench or socket ratchet to avoid wear and over-tightening, which helps preserve thread life.

Who It's For

This kit is aimed at homeowners, trailer owners, maintenance crews and small shops that need a reliable supply of identical U bolts for multiple fastenings or replacements. If you are assembling or repairing utility trailers, mounting square tubing, or securing wood beams, the included plates and nuts make installations straightforward.

Those who require precision or certified high-strength fasteners for heavy structural or safety-critical automotive applications should verify fit and strength requirements before relying on these bolts. Also, customers expecting custom sizes should confirm measurements carefully, as some users report mixed impressions about exact fit.

Pros & Cons

Pros

• Good value quantity with 15 bolts, plates and 30 nuts for extensive projects.
• Carbon steel with zinc plating provides solid corrosion resistance for outdoor use.
• Sized for 3 x 3 in square tubing, making selection simple for common trailer and tubing work.
• Includes matching frame plates which simplify secure clamping.

Cons

• Some customers report variance in perceived thickness or fit, so measure before committing to load-critical use.
• Not intended for applications requiring certified high-grade alloy fasteners.

Specifications

Our Verdict

For general purpose fastening where quantity and corrosion resistance matter, this 15-piece U bolt kit is a practical, cost-effective choice. It suits DIY trailer work, maintenance tasks and shop projects that need many identical clamps, but those needing certified high-strength fasteners or exact precision should confirm measurements and material grade before purchase.

Frequently Asked Questions

Are these U bolts suitable for outdoor use?
Yes, the carbon steel with zinc plating provides rust resistance suitable for outdoor and wet conditions.

Do the bolts include plates and nuts?
Yes, the pack includes 15 frame plates and 30 nuts so each bolt can be properly secured.

Will these fit 3 x 3 in square tubing?
They are sized for 3 x 3 in square tubing (3 in width), but measure your tube and check fit as some users report mixed experiences with fit and thickness.