Top Rated: Rab Sonic Range (SS, LS, Ultra) (7.8 / 10)
Category: Lightweight (Under 150g) Trekking Top (Updated)
The Rab Sonics are ultra-breathable, ultra-light zipped tees that self-identify as baselayers but have polyester chromosomes and no matter how much they think they're baselayers their fabric will always give them away.
The Sonics are extremely comfortable, have durable, low profile seams, soak up moisture well and dry rapidly. They pack away small and would make an ideal backup / spare for very long trips and won't weigh you down should you choose to carry them and wear a genuine baselayer instead.
In terms of the pricey Ultra, if you have the extra cash it's a nice minor upgrade (grab one when they're on sale and if you swoop at the right time, you should be able get them at least 40% off). The Sonic Ultra is a little lighter and has better ventilation and if your use-case is similar to ours, we advise sizing up.