At first glance, one could be forgiven for thinking the Rab Ascent 500 is just another nice-looking mummy bag. However, this is one for the enthusiast. With efficient use of space and technical fabrics, and a -5°C comfort rating – all in a 1060g package it takes performance beyond the outer edge of three seasons.

Wind- and down-proof polyamide (nylon) Pertex Microlite fabric is used inside and out. During testing an unexpected upward temperature shift left perspiration moisture lingering on the fabric’s surface before drying off, but for clarity’s sake it’s important to understand why this could happen. Rather than directly wicking moisture away as many other fabrics do, Microlite uses capillary action to disperse it across a wide area before moving it through. The Ascent is designed for multi-day excursions where gradual moisture build up and slow drying times could be problematic for a down bag. It’s in these conditions that the fabric and hydrophobically (water repelling) treated 650-loft duck down combine to increase water repellency, and reduces drying time by almost half as much again as untreated down. Although the most expensive of the bags tested, these qualities make the Ascent well worth considering for uncertain and inclement conditions.  

The bag is a well-proportioned, precise fit, while still roomy enough for comfortable movement. Thanks in part to the strategically placed adjustment cords, the head position is perfect inside the hood. At the other end, the slightly bulbous foot is roomy, allowing feet to rest naturally in their own warm locker. The low-level, three-quarter length side zip is backed by an excellent anti-snag strip, which allows the slider to glide smoothly through its length. The side draft tube is extended to provide a cover for the slider, but isn’t long enough to cover it completely, so it can touch your face when the hood’s drawn in. And the zip toggle rattles.

The Ascent is a more serious bag for the (although not exclusively) frequent user who may encounter a variety of conditions, particularly in the cooler months.