Over the years, I've worn many different types of baselayers from a variety of different manufacturers but in terms of wicking performance, these stand out as the best.
I use mine for walking, cycling, kayaking and as a general daily baselayer all year round. In chilly weather, I wear a merino wool layer on top: because merino doesn't wick as effectively as Helly Hansen's 'Dry' range, this provides the best combination of warmth and wicking without any clammy stickiness.
Worn alone in cold weather, they don't provide much warmth and they don't have much wind resistance either but they're not really designed as a thermal layer hence if you're standing around in cold temperatures then you're likely to feel cold. However, worn during activity then they are the best - sweat is wicked away quickly leaving your body still feeling (relatively) fresh but, most importantly, dry. (They're also perfect for dealing with menopausal hot flushes and night sweats too - although this isn't promoted on their sporty ads and packaging!)
They are true to size. I'm a UK 10-12 and ordered the small size. At first it felt tight due to the close fit but after a few hours, I'd completely forgotten about it as it stretches freely with every move. The close-fit is needed for the best wicking performance and the close-fitting sleeves don't ride up.
Because they wick sweat so effectively, they can be worn for several days without becoming smelly and after washing they they dry quickly too.
Definitely 5-star quality, fit, wicking performance and value for money.