Arc’Teryx ranks among my favourite brands for the design, cut and fabric choices, so I had high hopes for Phase SL. The combination of polyester and polypro is silky against skin with great moisture transfer. It is very lightweight and fast drying; predictably, once it had been through a few wash cycles, it also got smelly. The cut is comfortably close without being cheekily tight and the fabric is stretchy enough to feel completely unrestrictive. However, it has a short cut – between 4cm and 10cm shorter than the other performance base layers – so tended to pull out of legwear and ride up underneath a rucksack. Seams are flat-locked but have started to abrade slightly around the rucksack hipbelt area. There’s a tiny zip pocket on the back waist area, and it’s just high enough that it doesn’t clash with my pack. Phase SL is a good choice for high-energy days when you’re moving fast and light – and, for multi-days, will dry fast if you need to rinse out the whiff. I just wish it was slightly longer.