Best Mid Layer for Hiking, Backpacking, and Traveling (2026)

Arc’teryx’s Delta jacket is a lightweight fleece made from Octa wool, one of the newest high-tech fleeces to hit the market in the past couple of years. The name comes from the octopus-like fabric that creates air gaps, which helps trap in warmth while also allowing moisture to escape. It’s popular with ultra-light DIY brands, but Arc’teryx has adopted it for the 2025 revamp of the company’s popular Delta fleece jacket.

I hesitated to put this jacket in this guide, because although I like it as a very light midlayer for summer trips, there is an older, heavier version of the Delta jacket. Judging by the angry reviews on the Arc’teryx website, it was very popular. This jacket is something else entirely, but disgruntled fans of the older version aside, it’s a great midlayer for summer excursions, especially when worn with a sun hoodie. At 8.5 ounces for this, and 6 ounces for a sun jacket like the one from Kuiu below, you have a set that allows for multiple layering options and still weighs less than many of the more popular mesh fleece options. My only problem is that fashion was not taken into consideration when designing this jacket. One user comment on the Arc’teryx website likens it to a Mr. Roger jacket, which is almost true. But hey, it’s light and practical, who cares about fashion in the Outback?