My quest to find the ultimate summertime T-shirt for outdoor activity has led down many avenues. This month, the route took a turn and accelerated when it hit upon a shirt made by RailRiders, a Belmont, Mass., company with roots in the world of sailing.Today, RailRiders is more known in outdoor-adventure circles, and its clothing — which I have worn for years — is touted as the “toughest on the planet.” The company’s Eco-Speed-T is advertised to be quick-wicking, sun protective, and durable in the outdoors.I tested the shirt, which costs $36 and comes in men’s and women’s builds, in a six-hour adventure race last weekend. Temps peaked past 90 degrees and the sun blazed. I was soaked with sweat much of the day.The Eco-Speed-T at first might seem slightly too thick for hot days. It’s made of a nylon-polyester blend with a “waffle-weave” that gives it a tiny bit of bulk. But that’s where the wicking mojo comes from: Moisture and sweat are slurped off the body by this shirt and exposed to the air. At one point in the adventure race, I jumped in a lake to cool off. An hour later, after two miles of running and then 20 minutes in the wind on a bike leg, the shirt was almost bone dry.As an alternative to a cotton T-shirt, the RailRiders short-sleeve is an immense upgrade. There are mesh panels under the arms and up each side of the Eco-Speed-T for maximum airflow — a nice touch. The fabric is cited as offering UPF 20+ sun protection.The Eco-Speed-T also holds its own against some of my favorite hot-weather tops, including thinner synthetic and merino wool pieces that can cost twice as much. The thinner shirts at first feel airier than the RailRiders top, but in use they do not dry out as fast.In my quest for the perfect T, the RailRiders “waffle-weave” shirt is now near the top of my list. It’s a good value, and in my hot-weather test it proved its propensity to perform. Stephen Regenold is founder and editor of www.gearjunkie.com. Connect with Regenold at Facebook.com/TheGearJunkie or on Twitter via @TheGearJunkie.