Montane Phase Nano Review: A Lightweight Waterproof That Works Beyond Running

Introduction

The Montane Phase Nano is a three-layer Gore-Tex waterproof jacket that weighs just 250g for men’s and 220g for women’s sizes. It was designed as a fell-racing jacket but works equally well for anyone who wants a reliable, breathable waterproof that doesn’t add bulk to a pack or weight to a run.

What sets it apart is the choice of Gore-Tex Active, the most breathable membrane Gore-Tex currently manufactures. This membrane achieves a RET rating below three, making it exceptionally breathable while maintaining a 28,000 hydrostatic head waterproofing rating. Most lightweight running jackets compromise on one of these qualities to keep weight down. The Phase Nano does neither.

Who This Jacket Is For

This jacket suits runners, fell racers, and hill walkers who prioritize speed and packability without sacrificing weather protection. The design philosophy is straightforward: you should want to keep it on rather than stuff it away, because wearing it is more comfortable than most alternatives.

The Phase Nano is not marketed as a mountaineering jacket or a heavy-duty backpacking shell. If you regularly carry a heavy rucksack in sustained rain, a more durable option might be worth considering. For everything else—moving fast in the hills, day walks in changeable weather, or trail running in wet conditions—this jacket delivers genuine performance.

Gore-Tex Active Membrane and Waterproofing

The core advantage of this jacket is Gore-Tex Active. Most running waterproofs use cheaper membranes that sacrifice either breathability or waterproofing to keep costs down. Gore-Tex Active does neither.

The RET rating of below three is among the most breathable on the market. In practical terms, this means moisture vapour escapes quickly, so the jacket doesn’t feel clammy or sticky even during sustained effort. The 28,000 hydrostatic head rating is as waterproof as consumer jackets get. You are not trading waterproofing for breathability here.

The trade-off is durability. Gore-Tex Active is less robust than heavier Gore-Tex variants like Performance or Pro. The 13 Denier face fabric is thin and will not withstand the same abuse as an 80 Denier mountaineering shell. For a jacket designed to be worn, packed small, and moved in quickly, this is a sensible choice. For a jacket that will be dragged through rock and scrub regularly, it is a limitation worth acknowledging.

Design and Practical Features

The jacket keeps features simple. Hand pockets, a hood, bungee cuffs with no Velcro, and a hem with pull cords. Nothing unnecessary, nothing missing.

The hood is effective without being bulky. Three pull cords let you tighten it securely, and the wired peak keeps rain off your face in heavy downpours and wind. The bungee cuffs slide smoothly over thin running gloves and do not snag. The hem is cut short at the front to allow full leg movement but extends further at the back to cover your lower back and seat.

At 250g, the jacket rolls into a very small bundle. It will fit into a bum bag or the corner of a rucksack without taking up meaningful space. This packability means you are far more likely to carry it, which is the point.

Comfort and Wearability

The jacket’s backing fabric is notably soft and light. Wear it against the skin and it feels pleasant, not clingy or sticky. This matters because most lightweight running waterproofs feel uncomfortable when worn directly over a base layer, especially on warm or humid days. The Phase Nano avoids this problem.

The cut is designed for movement. It is short enough at the front to allow high leg drive when running, but long enough at the back to cover your seat and lower back. The overall fit is trim without being restrictive.

Because the jacket is so breathable and comfortable, you will likely wear it longer than you would a standard running waterproof. With a typical lightweight shell, you might remove it as soon as the rain stops because the clammy feeling becomes unbearable. With the Phase Nano, you may simply leave it on. This changes how you use the jacket and makes it more practical in changeable weather.

The jacket has received strong endorsements. It won best running waterproof in Trail Magazine in 2023, and experienced fell runners have praised it as a top choice.

Conclusion

The Montane Phase Nano is a well-executed lightweight waterproof that does not ask you to choose between breathability, waterproofing, and packability. It is not a jacket for heavy-duty mountaineering or sustained abuse, but for running, fell racing, and hill walking in variable weather, it is a genuinely strong option.