Is Fox Racing's new Union Boa shoe one of the lightest flat MTB shoes around?

Fox Union Boa Flat shoe in black
(Image credit: Fox)

Fox Racing has added the Union Boa Flat show to its Union shoe range. The new shoe joins the slightly later launched Fox Union Canvas and the rest of its MTB shoe line-up as Fox takes on the crowded mountain bike shoe category. It also sees the brand able to offer mountain bike riders full head-to-toe protection from the best mountain bike helmets to its full range of MTB apparel.

Fox also renewed its partnerships with its five Fox Diamond Bikeparks around Europe, which saw them add all-new Fox Trail features and extend the Fox Hot series that gives riding days with some of the Fox riders. The Fox Union Boa Flat look perfect for bike park days and I had a look over the details of its latest offering...

Muddy Fox Union Boa Flat shoes

Fox says the Ultratac rubber sole boasts best-in-class grip and durability (Image credit: Fox)

Weighing in at a claimed 327g per shoe, Fox says its new shoe is super light for a flat pedal MTB shoe. As an example, the tested Fox Union Flat laced shoe weighed in at 419g per shoe, and the also tested and best-in-test flat shoe – the Five Ten Freerider came in at 358g. Another rival shoe the Leatt MTB 2.0 shoe weighed in at a fairly feathery 332g. These comparisons are all laced shoes too, so the Fox claim of feathery performance seems fairly justified.

Up top, the Fox Union Boa Flat shoe has a one-piece upper aimed to deliver a consistent, precise fit. As the name of course suggests, it features a Dual Boa Li2 system that provides on-the-fly micro-adjustability. Fox says the precise fit, will deliver more power to the pedal through its molded internal stiffening plate. Adding that stiffness doesn't come at the expense of off-bike comfort, and are more than capable for those hike-a-bike moments, or post-ride chills.

They also feature a molded toe cap with a reinforced toe for protection against rock strikes, and the welded construction also protects from the elements.

Fox Union Boa Flat shoe in vintage white

The Fox Union Boa Flat shoes weigh in at a claimed 327g (Image credit: Fox)

Visually the shoe looks the same and features many of the details found in its siblings in the Union range. Bike Perfect Editor, Rich Owen, has tested the Union Flat laced versions and gave them top marks, saying they were an excellent option for flat pedal riders and they also fared well when pitched in against the Five Ten Freerider Pro.

From a price point of view, the Boa flats come in at a fairly hefty $224.95 / £209.99 / €224.99. In comparison, the laced version costs $149.95 / £129.99 / €149.99, and the Fox Union Boa clipless comes in at $249.95 / £219.99 / €239.99.

Elsewhere, these shoes feature an Ultratac rubber sole with an engineered tread pattern designed to provide best-in-class grip and durability. The low profile custom-tuned EVA midsole also improves pedal grip and feel, combined with the custom hex-shaped lugs on the sole are designed for maximum engagement with the best flat MTB pedal pins to deliver control and feel on the bike.

Pricing and availability

The Fox Union Boa Flat shoes are available now, sized from 37-47 with half sizes available from 41-46. Available in Black, Grey and Vintage White coloring, Fox also includes two pairs of arch height inserts to customize the fit. 

Priced at $224.95 / £209.99 / €224.99 with more information available at

Paul Brett
Staff writer

Based in Edinburgh, Paul Brett is a staff writer for He has been an avid cyclist for as long as he can remember, initially catching the mountain biking bug in the 1990s, and raced mountain bikes for over a decade before injury cut short a glittering career. He’s since developed an obsession for gravel riding and recently has dabbled in the dark art of cyclocross. A fan of the idea of bikepacking he has occasionally got involved and has ridden routes like the North Coast 500, Scotland and the Via Francigena (Pilgrim Route), Italy.

Current rides: Marin Alpine Trail 2, Ribble 725, Cube Stereo 160

Height: 175cm