Mac in a Sac Ultralite Running Jacket – Trail Tested Review (2025)

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.

Quick Overview

• Packs down small into its own pocket for easy storage on the go
• Waterproof to 8,000 mm, keeping you dry in heavy rain
• Breathable to 16,000 mm, preventing overheating during intense activity
• Fully taped seams ensure no water seeps through in wet conditions
• Stretch fabric allows for unrestricted movement while running or hiking
• Windproof design protects against harsh gusts and exposed terrain
• Adjustable hood with a wire peak offers a secure fit and added visibility in bad weather
• Eco-friendly construction, free from PFC and PFOA chemicals

My Experience with the Mac in a Sac Ultralite Running Jacket

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 the 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 will 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.

Mac in a Sac Ultralite Running Jacket Pros and Cons

Pros

• Both windproof & waterproof to keep you protected in harsh conditions.
• Stuffs into its own pocket for easy storage.
• Only 240g, which makes it ideal for running and fast-paced activities.

Cons

• No hood stowaway option, so the hood remains out when not in use.
• Limited color choices, a few more color options would be great.

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.

More Mac in a Sac Ultralite Running Jacket Photos

Learn More

Like this review? Well, you’re in luck as I’ve got a bunch of other great resources for you to explore here…

• Wild Camping: The Complete Beginner’s Guide
• Best Tents For Wild Camping
• Best Hammocks + Best Bivvy Bags
• Best Portable Camping Fire Pits
• Best Places for Wild Camping Wales, Scotland and The Lake District

I bought the Mac in a Sac Ultralite Running Jacket with my own money to test and review. My review is independent of the supplier and reflects my own unbiased opinions. Some of the links on this page are affiliate links, which means I may receive a small commission if purchases are made through those links at no additional cost to you. You can read my affiliate disclosure in the privacy policy.