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Rainmaster™ Underbody Boxes

Guaranteed 100% weatherproof and as durable as it gets.

HPI Rainmaster™ Underbody Boxes are full-faced underbody tool boxes that are equipped with an internal rain gutter. This makes for the ultimate water-tight underbody tool box for semi trucks and other rigs. Highway Products developed this style of internal rain gutter in the early 80s, and since has been copied by most other manufacturers because of its ease of manufacturing and functionality on the road. We recommend this style of underbody tool box when you need a completely weatherproof semi truck tool box.

HPI Benefits

The HPI difference is in the materials we use, the attention to all details and ultimately products we produce and proudly guarantee. Our promise is to take the best care of your product while we manufacture it, and continue to care for a lifetime after you receive it.

Lifetime Warranty

All of our products come with a Lifetime Warranty against defects in manufacturing (failed welds, etc.). It also includes all locking mechanisms, hinges, gas shocks, weatherstripping and any other materials we use. Learn More

Military Grade Aluminum

Highway Products uses nothing but the best materials. Our products are hand crafted out of Military Grade aluminum. Why take it that far? The days of using nothing but the best ingredients are all but gone in this world. We refuse to sink to that level. That’s the HPI difference.

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Hand-Made in the USA

Hand crafted from beginning to end right here in the USA. Every square inch of our products are touched by human hands, every step of the way.

Product Features

All HPI products come standard with options and features that you would normally pay extra for. Please explore all of our standard and optional features and call us with any questions you may have!

  • 5052 Smooth Aluminum
    We build our Rainmaster™ Underbody Boxes from rust-free 5052 aluminum, the same material used by the military, aircraft manufactures and boat builders.
  • T Handle Locks
    Our ergonomically designed T-Handle locks are the most secure locking mechanism on the market.
  • Watertight Seal
    We use Clean Seal™ automotive stripping around the edges of each toolbox to ensure a watertight seal.
  • Piano Hinges
    Piano hinges provide full-length support and reduces stress points caused by inferior hinges.
  • Reinforced Strength
    Highway Products tool boxes are reinforced and reinforced again. That's why they last for millions of miles. We didn't get our reputation from skimping. Our underbody boxes are built with Herculean strength.
  • Stainless Steel Torx Screws
    Stainless steel Torx screws are the toughest fasteners on the market today. These fasteners won't loosen as you drive down the road and a door can be replaced without a special rivet gun.
  • Angle Bracing
    One of the weak points of truck tool boxes is the bottom corners. There is so much road stress from carrying heavy tarps, chains, tools, and other equipment, the corners sometimes break. Highway Products has eliminated this problem with reinforced angle bracing welded in the corners.
  • Pull Out Drawers
    Great organizational tool - we can make them in any size and we have different weight capacities to meet your needs.
  • Optional Dividers
    A divider option placed on one side of the underbody tool box keeps tie-down chains from drifting around the tool box, plus a hanging bar.

Rainmaster™ Underbody Boxes Videos

Rainmaster™ Underbody Boxes Images

Hpi Black Diamond Plate

HPI Black Diamond Plate

Our signature HPI Black Diamond Plate finish combines that trendy satin look with just a little shine to hide scratches and keep that tough black look.

Diamond Plate

Diamond Plate

Tried and true. The all time classic finish. Rugged, durable and will last forever.

Leopard

Leopard Finish

HPI's signature finish. Black powder coated diamond plate with hand shaved diamonds. If there's a better look on earth, we'd love to see it!

Gladiator

Gladiator

Another HPI exclusive finish. Raised dimples for texture and to hide scratches. Available in raw aluminum or powder coated.

Hpi Black

HPI Black

Our signature HPI Black finish combines that trendy flat look with just a little shine to hide scratches and keep that tough black look.

Custom

Custom Colors

Custom colors? You bet we do that! Whether you need a color match, want something to stand out or blend in, we can cover it.

Interested in our Rainmaster™ Underbody Boxes?

Our team of Product Specialists are on standby to answer any remaining questions you have about our Rainmaster™ Underbody Boxes or to assist you in placing your order.

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