Mac in a Sac made its name with packable everyday waterproofs. The Ultralite Running Jacket takes that idea onto the trails – with a breathable, seam-sealed shell that’s light enough to carry on long-distance runs.
Thanks for your support – I may earn a small commission from affiliate links in this article Learn more
The Mac in a Sac Ultralight Running Jacket was purchased at full price by me. All opinions are my own.
- Build Quality
- Performance
- Features & Usability
- Value for Money
The Verdict
The Mac in a Sac Ultralite Running Jacket does exactly what a trail running jacket needs to do: it keeps you dry, lets you breathe, and disappears into your kit when the sun comes out. I wore it on a wet Peak District loop in wind and rain, and it didn’t let a drop in. The breathability is the real surprise — this doesn’t feel like you’re running in a bin bag. My only gripe is the hood, which stays out when you unzip rather than stowing neatly away. But if you’re after a lightweight, packable waterproof that’ll earn its place in every running vest, this one’s worth serious consideration.
Pros
Cons
Where to Buy
Ultralite Running Jacket
My Verdict: “If you’re looking for a lightweight, breathable, and genuinely waterproof running jacket that won’t weigh you down, this one’s hard to beat.”
Women’s version also available at
Mountain Warehouse, Decathlon, and Amazon.
Best For: Trail runners and hikers wanting a lightweight, packable waterproof layer
Price: £74.99
Weight: 240g (size M)
The Mac in a Sac Ultralite is a 2.5-layer running jacket built for high-output activities. It’s waterproof to 10,000mm and breathable to 16,000gsm, with fully taped seams that keep water out even in sustained rain and a windproof, stretch fabric that allows unrestricted movement while running or hiking.
At just 240g it packs into its own pocket for easy storage on the go, the adjustable hood has a wire peak for a secure fit and added visibility in bad weather, and the whole thing is built without PFC or PFOA chemicals.
Tested across the Hen Cloud and Roaches loop in the Peak District, in wind and rain, along with many other training runs in the South East.
Ultralite Running Jacket Specifications
| Spec | Detail |
|---|---|
| Price | £74.99 |
| Weight | 240g / 8.4oz (size M) |
| Waterproof Rating | 10,000mm (see correction note above) |
| Breathability Rating | 16,000gsm |
| Construction | Vapourlite 2.5-layer |
| Material | 96% Polyester / 4% Spandex |
| Seams | Fully taped |
| Fit | Close fitting |
| Hood | Adjustable with wired peak |
| Pockets | 2 front zipped pockets (right doubles as stuff sack) |
| Cuffs | Partially elasticated |
| Hem | Toggle adjustable |
| Sustainability | PFC-free and PFOA-free |
| Reflective Details | Yes |
| Available | Men’s and Women’s, XS–XXXL |
| Colours | Black, Blue, Neon Orange, Navy + others |
My Experience with the Mac in a Sac Ultralite Running Jacket
At the start of 2025, I was on the hunt for an ultralite running jacket as trail running had become my latest obsession after signing up for Man vs. Coast, an adventure race well beyond my comfort zone.
With a seam-sealed waterproof jacket on the mandatory kit list, I needed something breathable, packable, and built for long-distance trails. I finally found what I was looking for at the National Outdoor Expo when I came across Mac in a Sac.
Originally, I had my eye on one of their standard waterproof jackets, but after chatting with the team and explaining my running plans, they recommended their Ultralite Running Jacket. It didn’t take much convincing; this jacket ticked all the right boxes. The hardest decision? Picking a colour.
Straight after the expo, I headed north to the Peak District to test the jacket on a long Sunday run. I chose a challenging loop starting at Hen Cloud, running towards The Roaches, descending through the forest, and passing through Lud’s Church, an incredible natural wonder that felt like running through Jurassic Park—before circling back to my starting point. The weather was far from ideal, windy and wet. But that made it the perfect opportunity to put the Ultralite Running Jacket through its paces.
I started my run in just a t-shirt and a jacket. As I climbed Hen Cloud, the wind was so strong it nearly knocked me over, but the jacket kept me protected and comfortable. Running across The Roaches, I hit light rain showers, and the water simply beaded and rolled off.
One of my biggest concerns with any running jacket is breathability, there’s nothing worse than feeling like there’s more condensation inside your jacket than rain outside. Fortunately, this wasn’t an issue. The Ultralite kept me dry from both sweat and rain, maintaining comfort throughout the run.
I wore the jacket for the first 6K before the clouds parted and the day started warming up. When I took it off, I was impressed by how easily it packed down into its own left pocket. Once packed, it fit neatly into my small running vest, and I barely noticed the extra weight in my pack.
There are also a few design details I really appreciate. The cuffs have a unique construction, smooth across the back of the hand with elastic only on the underside of the wrist. I’m not sure what the functional benefit is, but it feels great and avoids any tight or restrictive pressure.
The hood sits snugly around my head and features an elastic fastener at the back, allowing for easy adjustments. When fully zipped, the collar covers my chin, providing full protection in harsh weather.
I also picked up the Mac in a Sac Ultralite Waterproof Cap, another piece in their Venture Series, which pairs perfectly with the jacket. Worn under the hood, it adds an extra layer of protection against wind and rain.
Overall, the Ultralite Jacket performed brilliantly in challenging conditions, proving itself as a lightweight, breathable, and highly packable piece of kit that I’ll be sure to come out on every run moving forward.
You always know when you’ve found a great piece of gear because you forget it’s even there, it just fits seamlessly into your activity. That’s exactly how I feel about the Mac in a Sac Ultralite Running Jacket.
Although designed for active sports, I can see myself using it for casual day trips with the family, too, thanks to its lightweight, packable nature.
Where to Buy
Ultralite Running Jacket
My Verdict: “If you’re looking for a lightweight, breathable, and genuinely waterproof running jacket that won’t weigh you down, this one’s hard to beat.”
Women’s version also available at
Mountain Warehouse, Decathlon, and Amazon.
More Mac in a Sac Ultralite Running Jacket Photos
Related Guides & Reviews
Like this review? Well, you’re in luck as I’ve got a bunch of other great resources for you to explore here…
- Berghaus Maitland GORE-TEX Overtrousers Review
- Mac in a Sac Ultralite Waterproof Trousers Review
- Best Waterproof Jackets for Hiking in the UK
- Best Gore-Tex Jackets for Hiking in the UK
- OEX Kintra Hooded Down Jacket Review
Steve Cleverdon
Adventure-driven outdoor gear reviewer and paddleboarder, Steve has spent 20 years exploring rivers, coastlines, and trails across Britain and abroad, sharing what he’s learned along the way. Learn more about Steve or get in touch.
