A light insulated gilet is one of the more versatile bits of outdoor clothing, equally useful as a summer warmth booster, worn within your winter layering, or carried just in case. Lacking sleeves, these vests are lighter and more packable than the equivalent jacket would be, a factor that'll appeal to weight conscious backpackers and mountaineers; they can also allow freer arm movement, which is clearly good news for climbing and scrambling.

I'm a vest fan, and be it a quick evening at the crag, a hillwalking trip, or a day of winter mountaineering, I'll pack one more often than not. Mammut's Rime Lite IN Flex Vest (long name for something this simple) is pretty much bang-on for all these uses and more. 

In use

Weighing just 210g (size M) the Rime Lite Vest (for short) is minimalist for an insulating layer, taking up little space in a compact summer hill pack, an overnight backpack or even a running vest (here's where things might get confusing - perhaps we should call this top a gilet?). It stuffs into one of its own pockets for easier packing, and the only drawback from a climbing perspective is that this lacks a loop for hanging off your harness.  

Being only lightly insulated, this gilet is great to wear on the go when you want just a little warmth but not too much heat or bulk. It feels suitably breathable and quick-drying, thanks in part to large stretch-fleece side panels which let in the air, and I've yet to feel stuffy in it when hillwalking in cool summer conditions.

I think it's the perfect weight and thickness for an all-round, wear-all-day layer, something that's going to be equally useful for pretty much any mountain or climbing-related activity. So far I've worn mine for hill days and climbing, and I can't think of many occasions when I wouldn't consider it either as my main insulation on the move, a backup layer in the pack, or as part of a warmer layering system. It's likely to see service winter climbing when that season rolls around, and I may well use it for core warmth when running in cold weather too.

Fit

Mammut make the Rime Light Vest in both men's and women's versions. Though described as an athletic fit I'd say it has a generous cut for the stated size, and at 183cm tall (and not skinny) I found I had to go down from my customary L to a size M; this is clearly a case of try before you buy, since you want a reasonably close cut in a gilet for easy layering. On me this downsize is pretty much bang on, fitting closely enough to feel neat over just a t-shirt, and not too bulky beneath a shell, while still allowing enough room to add a midweight fleece underneath - a combo that I think can be brilliant in winter.

Jackets and midlayers often seem to come out a bit short on me, but in this case there's enough length in the hem for below-waist snugness, and I do definitely prefer a slightly longer cut like this. Since there are no sleeves, arm movement is unhindered and I get very little hem lift with raised arms - a frequent bugbear for climbers. The arm holes are quite close-fitting to keep the warmth in, but with enough stretch for comfort.

The collar comes high for maximum neck coverage, and for neater layering it's probably good that this will be at least one hoodless item in your wardrobe, since so many tops and jackets seem to come with a hood these days (making for a bulky feel once you're wearing a couple). Overall I'm really happy with the fit.

Fabric and fill

With a thin-but-sturdy 20D nylon outer fabric, the Rime Lite Vest doesn't seem at all flimsy for something this light. The fabric is reasonably wind-repellent, keeping out at least the worst of a summit breeze, and has a slight give that aids the general unrestricted feel. For max breathability Mammut have used a Pertex Quantum Air lining, which is appropriately unsweaty when you're on the go.

As for insulation, you get 40g/m2 of synthetic fill, offering decent warmth with very little bulk and weight, and this too has a wee bit of stretch. For a light gilet designed for active wear I think the amount of insulation is spot on, covering the front and back of the body to provide core warmth without overdoing things. Big side panels of very stretchy Polartec Power Grid fleece are great for freedom of movement, and for allowing plenty of breeze to pass in and sweat to escape.

Pockets and zips

Roomy enough for hat and gloves, the two zipped hand pockets are placed high enough to remain usable under a rucksack hipbelt or a harness. The chunky main zip feels robust, and comes with a glove-friendly zip pull and a second zipper to allow you to open the front from the bottom - not something I've ever wished for in a gilet, but maybe someone will.

Ethics and environment

This is a Bluesign product, and Mammut are members of Fair Wear.

Summary

Light, breathable, well cut, stretchy for free movement, and an ideal thickness to provide just a little insulation without boiling you when you're on the go - the Rime Lite IN Flex Vest is a versatile layer that would be useful in pretty much any mountain or climbing-related setting, year round. It's not cheap (what is, these days?) but if you're after a minimalist insulated gilet then this one really is hard to fault.