What does it take to improve a classic?  One formula is to keep all the great features of the original, then add a bit more functionality.  Nathan demonstrates this technique to perfection with the new Zelos 2L Hydration Vest.

Nathan Zelos Hydration Vest Features:

  • Weight: 18 oz / 510.3 g (includes bottle and bladder)
  • Storage capacity: 531 cu in / 8.7 L without bladder
  • Equipped with one 18 oz / 535 mL SpeedDraw Flask
  • Two front bottle pockets and one front zip smart phone-compatible pocket
  • Stash pocket over left front pocket fits several gels
  • Pill pocket for electrolyte tabs
  • Gusseted stretch mesh rear pocket for increased capacity
  • Internal stash pocket and key clip
  • Hydrapak reversible 70 oz / 2L fluid reservoir
  • Rear external shock cord
  • 3-way propulsion harness to stabilize movement of bladder and cargo
  • Adjustable height sternum strap and drink tube clip
  • Wall mesh shoulder straps
  • Perforated back panel for breathability and weight reduction
  • Reflective trim
  • Two color options
  • MSRP $125

nathan zelos running

My New Favorite Race Vest?

An important point of reference before jumping into the review: for almost as long as I’ve been an ultrarunner, my go-to training vest has been Nathan’s iconic HPL 020.  Through the years, I never thought I’d find a pack that offered a better combination of lightness, comfort, and functionality … until I started testing Nathan’s Zelos pack, that is.

nathan zelos front

The jury’s still out on its multi-year performance, but after a few hundred miles and a couple dozen training runs, I can confidently say that the Zelos has become my new go-to training vest.  There’s a slight tradeoff in weight – 18oz for the Zelos vs 13oz for the HPL 020* – but in exchange you get a lot more cargo storage and functionality without sacrificing comfort on the long run.

(*The weight difference is less if you leave the water bottle at home, as I typically do.  In that case, the pack weight is closer to 16 or 15 oz instead of the spec 18.)

18-oz Nathan SpeedDraw flask on R; standard 20-oz bottle on L.

18-oz Nathan SpeedDraw flask on R; standard 20-oz bottle on L.

From a storage standpoint, the Zelos gives you a lot of options on the front of the vest, which is great if you prefer (as I do) to carry your critical cargo in a way that is easily accessible.  Dual front bungee pockets are large enough to carry water bottles, which is the trend in many packs lately.  The SpeedDraw flask that comes with the vest is sleek and slightly lower in capacity compared to traditional water bottles, but standard 20-oz bottles fit in the pockets easily as well.

nathan zelos front pockets

Of course, if you are carrying fluid in the reservoir, that allows you to free up the front bottle pockets for more gear.  One bungee pocket can easily hold several gels or blocks, or larger items like a map or camera.  Additional pockets on the front straps provide storage for a smartphone, a stash pocket for empty gel wrappers, and a waterproof pill pocket for electrolyte or salt tabs.

nathan zelos rear compartments

On the back side, the storage area extends the entire vertical length of the pack, rather than stopping halfway down as the HPL 020 does.  It’s more than enough room for a lightweight jacket to fit into, and there’s still storage capacity in the reservoir compartment to store a hat, gloves, and headlamp after the sun comes up.  And if your top layer is too bulky to fit in the pocket, the external bungee will keep it securely in place.

A Comfortable Ride

From a comfort standpoint, the Zelos rides just as smoothly as the HPL 020, with lightweight mesh throughout the straps and back panel to maximize breathability.  The three-way harness system can be adjusted for customized tightness, but here is one quibble I have with the pack: the straps seem excessively long after they’ve been set at a mid-range setting.  I like to think I have an average-size torso, but my preferred harness positioning leaves several inches of loose straps to tie off or tuck in somewhere.

nathan zelos drink tube

Drink tube exit route over R shoulder

Another critique is that the Zelos doesn’t offer a center tube-exit option from the reservoir compartment – the pack is designed so that the drink tube can only exit over the right shoulder.  Right is my preference, so this isn’t a big deal, but if you’re a left-shoulder drink tube guy, this will be a source of frustration.

hydrapak reservoir

However, the reservoir itself is a major strength of the Zelos; like all Nathan packs, it uses a reversible plug-and-play bladder from Hydrapak, who set the gold standard with reservoir construction.  The 2L bladder is easy to fill and close, and even easier to clean when the run is over.

The Good:

  • Outstanding combination of lightweight comfort and functionality
  • Several cargo storage options on front straps
  • Hydrapak reversible reservoir is durable, and easy to use and clean

The Bad:

  • Harness straps seem too long and can be annoying if unsecured
  • No center drink tube exit option

The Bottom Line

The improvements in functionality and storage space in the Zelos more than offset the small increase in weight compared the HPL 020.  If you’ve been a fan of Nathan’s classic race vest, you owe it to yourself to give the Zelos a try – you might discover you have a new favorite.

Buy Now: Available at REI

About Author

Donald is a physical therapist, ultrarunner, barefoot aficionado, and father of three with more than 20 years of experience in endurance sports. When he's not training for ultramarathons, he enjoys hiking or slacklining with his family in Monterey County, CA.

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