By STEPHEN REGENOLD

My quest to find the perfect fitness training T-shirt has come closer to a conclusion. The NBx Burnout Tee from New Balance is made of recycled polyester and an exotic fabric derived from coconut shells. For running and other sweaty aerobic activities, this airy shirt is my current Holy Grail.

Indeed, no other top I own breathes so well. The company’s mix of the coconut-based Cocona fabric, a polyester mesh, and reflective piping to improve visibility have added up to an ultimate top I’ve employed this year dozens of times.

New this past spring, the NBx Burnout Tee is touted to provide evaporative cooling, odor resistance and UV sun protection. New Balance (www.newbalance.com) calls it perfect for “rigorous training workouts.”

I have run in the shirt on days above 90 degrees. But I also hiked 25 miles on a backpacking trip in New York’s Catskill Mountains wearing the top. It served as my jersey during an eight-hour adventure race in July.

Throughout all these activities, the shirt proved to be comfortable and breathable even when soaked with sweat. The Cocona fabric seems to be the secret ingredient. Though it is a mesh, it has a rougher feel than a nylon or polyester. Cocona is akin to a fine wool T-shirt, though the husk-based fabric breathes better than most wool I have used.

New Balance sells the NBx Burnout Tee for $45. It’s currently priced at around $35 on some web sites. For my nightly neighborhood training runs, to bike rides, backpacking trips, and races, the Burnout Tee has been my shirt of choice this summer and fall.

—Stephen Regenold writes about outdoors gear at www.gearjunkie.com.