If you’re setting out for a run in hot weather, that favorite cotton tee isn’t the best choice. Cotton looks great, sure, and most of the time it feels terrific. But with low breathability and a knack for absorbing and retaining moisture (i.e., sweat), cotton tops used for running grow and stay wet, irritate skin, and can get smelly.

That’s why the new generation of “tech shirts” — running tops made of synthetic materials — have become popular. Because they’re breathable and sweat-wicking, they dry quickly and won’t chafe your skin (and since your sweat dissipates rather than hang around, odor doesn’t develop). And since they’re light in weight and built for free movement, you’ll scarcely know they’re there.

A limitless selection of tech tops is available, but here are two that have proven to be strong favorites among runners:

Brooks Stealth Short Sleeve for Women: Made from 100 percent featherweight polyester, the Stealth top has a fitted look but offers unrestricted full-range motion and is a fast-drying sweat-wicker. With cap sleeves, a V-neck, and a subtle Brooks logo on the upper left shoulder, the design is sleek and simple. Comes in five colors. $45. There’s also a women’s tank version ($40, four colors). www.brooksrunning.com.

Patagonia Nine Trails Shirt for Men: This handsome tech tee looks and feels like heathered cotton, but it’s made from 100 percent polyester and has been treated with Polygiene odor control. It weighs 4 ounces, sports a locker loop that lets you hang it up practically anywhere to dry, and the front-of-the-shirt logo is reflective. Set-in sleeve construction with underarm gussets permits free range of motion and prevents chafing. Comes in 5 heathered colors. $45. www.patagonia.com.

In Sonoma County, Patagonia products are carried by Dick’s Sporting Goods, Sports Basement and REI; Brooks products can be found at Fleet Feet Sports, Heart & Sole Sports, Athletic Soles, Dick’s Sporting Goods, Sports Basement and REI.