After getting plenty of use out of my Mac in a Sac Ultralite Jacket, picking up the Ultralite Waterproof Trousers felt like the natural next step to complete my waterproof running kit. I’ve now put them to the test on a few wet and windy trail runs, and here are a few of my thoughts on how they’ve performed.
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Quick Overview
Best for: Trail runners and active hikers who run hot and need breathable, waterproof legwear.
Price: £65
The Mac in a Sac Ultralite Waterproof Trousers are part of the brand’s Venture Series — their performance-focused range built for runners and fast-paced outdoor use. Made from Vaporlite fabric (90% polyester, 10% spandex), they combine a 10,000mm waterproof rating with 16,000gsm breathability, fully taped seams, articulated knees, and quarter-length leg zips. They pack down into a compact bundle using an internal elasticated loop.
Tested across multiple wet trail runs around Sussex while training for Man vs Coast
Mac in a Sac Ultralite Waterproof Trousers Specifications
| Specification | Detail |
|---|---|
| Fabric | Vaporlite — 90% Polyester, 10% Spandex |
| Waterproof Rating | 10,000mm |
| Breathability Rating | 16,000gsm |
| Seams | Fully taped |
| Weight | ~130–165g (varies by size) |
| Colours | Jet Black |
| Lengths Available | Regular, Long |
| Sizes | S, M, L, XL, XXL |
| Waist | Elasticated with drawstring |
| Leg Zips | Quarter-length (for pulling on over shoes) |
| Reflective Details | Logo (left thigh) + strips on leg zips |
| PFC/PFOA Free | Yes |
| Windproof | Yes |
| Quick-Drying | Yes |
At 10,000mm waterproofing and 16,000gsm breathability, these sit comfortably above the average for lightweight running waterproofs — you’d normally expect to sacrifice one for the other at this weight and price point.
My Experience with Mac in a Sac Ultralite Waterproof Trousers
I’ve been putting the Mac in a Sac Venture Series Ultralite Waterproof Trousers through their paces over the past few weeks while training for Man vs Coast around Sussex, and honestly, they’ve really impressed me. You’ll probably know how I am with the Mac in a Sac Venture series – I’m a proper fan of their gear – and these trousers definitely don’t disappoint.
So here’s the thing about testing waterproof running gear in Britain – you get plenty of opportunities! I’ve been caught in some proper downpours during my training runs, and these trousers have kept me completely dry every single time. What’s really stood out is how breathable they are. The thing is, I run pretty hot, so I’m quite picky about when I’ll actually wear waterproof clothing, usually only in heavy rain. But these have been brilliant because they let moisture and sweat escape really well, so I don’t get that horrible clammy feeling you usually get with cheaper waterproof kit.
The quarter-length zips on each leg are ideal for quickly putting on the trousers when the heavens open up – you can easily slip them on over your running shoes, though, that said, I would probably avoid doing it with muddy trainers if you don’t want the inside caked in mud. The elasticated waistband sits really comfortably and doesn’t ride up when you’re running, plus there’s a drawstring if you need to adjust the fit further. I’m wearing a small, which is my usual size, and the fit is spot on.
One thing that’s really impressed me is how quiet they are. You know that annoying swishing sound you get with most waterproof trousers? These are virtually silent when you’re running, which makes such a difference on longer sessions. The reflective bits are well placed too – there’s the logo on the left thigh and strips on either side of the leg zips, so you’re nicely visible for those early morning or evening runs.
As with all Mac in a Sac gear, the packability is well thought out. There’s this little elasticated loop inside the waistband to loop around the trousers once rolled up, keeping them compact in a tiny bundle. Perfect for shoving in your pack when the weather looks dodgy – you know how quickly it can change around here!
From a technical point of view, they’re made with Mac in a Sac’s Vaporlite fabric, which is 90% polyester and 10% spandex, and they’re fully seam sealed. There’s actually quite a cool contour pattern on the inside, too, which is a nice touch. The zips look standard rather than waterproof, but to be honest, that hasn’t been an issue in any of the wet weather I’ve tested them in.
What I really love about these is that they feel like proper running trousers rather than just waterproof overtrousers you’re putting up with. The stretch fabric moves with you naturally, the elasticated cuffs at the bottom give you that streamlined fit without any flapping about, and the whole thing just feels well thought out. They only come in black, but that works for most people’s kit anyway.
Look, like everything else in the Mac in a Sac Venture series, these just work really well. They’ve become a regular part of my training kit, and I’ll definitely be taking them to Man vs Coast in a few weeks. If you’re after reliable waterproof running trousers that don’t compromise on comfort or performance, these are definitely worth considering. They prove you can have something that’s both ultralight and properly protective, which is exactly what you want when you’re out training in unpredictable British weather!
- Build Quality
- Performance
- Features & Usability
- Value for Money
The Verdict
The Mac in a Sac Ultralite Waterproof Trousers do what the best lightweight kit always does — they stay out of your way. You put them on, stay dry, stay comfortable, and forget they’re there. The 10,000mm/16,000gsm spec combo is impressive, and the stretch fabric means they feel like running kit rather than an emergency cover-up you’re tolerating. The lack of pockets is the one niggle, and they’re not a substitute for a full-spec hiking overtrouser in sustained extreme conditions. But as a trail running and fast-paced hiking waterproof for British weather? They’re a solid buy.
Mac in a Sac Ultralite Waterproof Trousers Pros and Cons
Pros
- Great balance of waterproofing and breathability for active use
- Lightweight feel but still durable enough for rugged terrain
- Perfect fit for my height (163cm, regular size)
Cons
- No pockets, so you’ll need to stash essentials elsewhere
- Can feel a little warm if worn over thicker base layers
More Mac in a Sac Ultralite Waterproof Trousers Photos
Mac in a Sac Ultralite Waterproof Trousers FAQs
Related Guides & Posts
The resources below cover the basics, common questions, and related kit to help you get more out of your time in the wild.
- Mac in a Sac Ultralite Cap Review – The Perfect Running Cap?
- Mac in a Sac Speedpro Waterproof Backpack Review
- Berghaus Maitland GORE-TEX® Overtrousers Review
- Best Waterproof Jackets for Hiking in the UK
- Best Gore-Tex Jackets for Hiking in the UK
I was kindly gifted the Mac in a Sac Ultralite Waterproof Trousers to test and review. My review is independent of the supplier and reflects my own unbiased opinions.
About the Author
Steve Cleverdon is an outdoor adventure specialist with 15+ years of hiking, camping, and paddle boarding experience. He has conquered Europe’s toughest trails including the GR20 in Corsica, walked 3,000km solo across New Zealand, and worked professionally in the outdoors industry. Steve’s gear reviews and recommendations are based on real-world testing across four continents, from coastal waters to mountain peaks. Learn more about Steve or get in touch.
