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
- Ultralight and flexible Vaporlite fabric for full mobility
- Waterproof to 8,000mm with fully taped seams
- Breathable rating of 16,000gsm for all-day comfort
- Windproof and quick-drying in changeable conditions
- Elasticated waist and articulated knees for a secure fit
- Packs down small with built-in storage loop

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!
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
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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. 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.

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.