The RZR 900 and 1000S were never given a bed, and every owner solves that the same way at first: a soft bag strapped behind the seats, a cooler bungeed to the cage, tools in the footwell. It works until the first river crossing or the first long dusty haul, and then you find out what “water resistant” meant on the tag. The Moto Alliance HIGHLANDS Custom Rear Cargo Box is the hard-sided answer for these machines, and it is $469.99.
37 gallons, 25 pounds
The numbers Moto Alliance publishes are the reason to look at this one: 37 gallons / 148 quarts / 140 liters of capacity at a lightweight 25 pounds, which they call industry leading capacity for the platform.
Those two figures matter together rather than separately. Capacity on its own is easy — anyone can bolt a big box to the back of a machine. The weight is what decides whether you leave it on. Twenty-five pounds hanging behind the rear axle on a 900 or 1000S is noticeable but livable; a steel box twice that weight changes how the machine rides and how the rear shocks behave, and it ends up in the garage by midsummer.
For scale, Moto Alliance says it is large enough for helmets, clothing, tools and more. Helmets are the honest benchmark, because a box that will not swallow two helmets is a box you still have to work around.
Built to be hit
The box is molded from impact-resistant, low-density polyethylene to withstand any terrain. Low-density polyethylene is the right material choice for this job and it is worth knowing why: it deforms and springs back rather than cracking. A rigid composite box looks better on the shelf and splits at the mounting points after a season of whoops. A molded LDPE box takes a branch strike, dents, and carries on.
Moto Alliance describes it as heavy duty and weatherproof with a custom OEM fit, with an OEM finish custom fit to the lines of your RZR. That last part is the difference between a cargo box and a universal tote with brackets — it is shaped for this machine, not adapted to it.
Sealed and locked
The box uses weatherproof seals and lockable latches, which Moto Alliance says will make sure your gear is dry, dust-free and secure when you reach your destination.
- Dry is the seal doing its job in rain and water crossings.
- Dust-free is the one that surprises people. Fine dust gets through anything that is not actually sealed, and it is what ruins cameras, radios and spare clothing on a desert ride.
- Secure is the latches. A locking box is what lets you leave the machine at a trailhead or outside a cabin and walk away.
On and off in minutes
Moto Alliance builds this with a quick release system — install and remove in minutes, no tools required.
This is the feature that decides whether a cargo box gets used. A box that needs a wrench on each corner lives on the machine permanently, including on the days you want the weight off for a fast trail ride or need the space for passengers and gear at a staging area. Being able to pull it in the parking lot and drop it in the truck is what makes a 37-gallon box practical on a sport machine rather than a permanent commitment.
Fitment
Moto Alliance lists this box for:
- 2015-2026 Polaris RZR 900 and 1000S, all standard and Trail models
That covers the RZR 900, RZR S 1000 and RZR Trail S 1000. It is a wide window — eleven model years on one part number — which tells you Polaris did not change the rear structure on these machines much over that run. Still check your year and model against the listing before you order.
Who it is for
Owners who camp, hunt or ride far enough from the truck that gear has to come along, and anyone currently running a soft bag who has already lost a round to water or dust. It is also the right call for a machine that does double duty on a property, where tools need to live on board and stay locked up between jobs.
Order it at SxS Outpost
The Moto Alliance HIGHLANDS Custom Rear Cargo Box is $469.99 and ships direct from Moto Alliance with their warranty. Confirm your year, make and model on the product page before ordering. Browse the rest of what fits in the Polaris RZR S 1000 and Polaris RZR 900 collections, or compare every option in Storage & Cargo.