An in-depth review of the Black Diamond Rhythm T-Shirt.

If you are looking for a light and comfortable t-shirt that can take you from the trails to town without skipping a beat, the Black Diamond Rhythm T-Shirt ($90) is an excellent choice. This merino-blend tee is super light and has the wicking ability of synthetic material and the comfort and anti-odor properties of wool. A Soft See Through Fabric

This shirt is stretchy, light, durable, and has a slim fit. There are men’s and women’s versions available. The men’s sizes range from small to extra large, and women’s range from extra small to extra large. It is a stylish, quick-drying shirt that is perfect for long runs, multi-day adventures, and travel days alike.

So many members of iRunFar’s test team enjoy this shirt so much that we named it a top shirt in our best running shirts for women, best running shirts for men, and best wool running apparel guides.

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The Black Diamond Rhythm T-Shirt.Photo: iRunFar/Eszter Horanyi

The Black Diamond Rhythm T-Shirt is made of a blend of merino wool and nylon. The natural wool fiber from merino sheep is inherently good at temperature and moisture regulation, making it a great choice for activewear. The material is odor resistant and porous, and it allows sweat to escape as a vapor to keep you dry. Merino wool is much softer than traditional wool, so your running shirt won’t feel scratchy on your skin.

This shirt features a blend of 57% nylon and 43% merino wool. The fabric, which Black Diamond calls NuYarn, consists of a nylon core wrapped with merino fibers. This blend is a lighter, stretchier, and more durable fabric than 100% merino wool, and it also dries much faster. The construction of the fabric keeps merino fibers close to the skin to capture the temperature-regulating and odor-resistant properties merino is so well known for. The blend is also great for durability, and after more than 1.5 years of regular use, our shirts look just as they did on day one.

A front view of the Black Diamond Rhythm T-Shirt. Photo: iRunFar/Meghan Hicks

Black Diamond calls the Black Diamond Rhythm T-Shirt “the world’s lightest technical merino wool shirt.” The iRunFar team wholeheartedly agrees that this shirt is light as a feather, practically disappearing when on your body. It is a slim fit, but the NuYarn material provides a good amount of stretch so that it moves comfortably with our stride. It never feels too tight or compressive.

We’ve run in this shirt in steamy hot summer weather and chilly days, and it kept us comfortable across various temperatures and humidity levels. We did find the limits of the shirt’s humidity comfort level in our testing, however. When the temperature and dew point were the same, this shirt felt like too much material. Still, under most conditions, its horizontal ribbing kept it from feeling clingy in warm weather, and it kept us warm and well-insulated on cooler days.

The material wicked away moisture and dried incredibly quickly. It didn’t absorb salt from sweat, and there was none of the stiffness or crusting caused by abrasive, dried salt patches that we have experienced with some synthetic running shirts.

This became the first shirt many on the iRunFar team reached for when heading out for multi-day outings or long trips when laundry days may be scarce. It stood up to daily use for seven days straight for one user and didn’t stink by the end of the week. It hand washes well, which gives it extra points for travel when sometimes you’ve got to do your own laundry.

A back view of the Black Diamond Rhythm T-Shirt. Photo: iRunFar/Meghan Hicks

The Black Diamond Rhythm T-Shirt is a top choice for us in our best running shirts for women, best running shirts for men, and best wool running apparel guides. It has a great balance of light weight, stretch, wicking capability, and temperature regulation that makes it comfortable for both hot and cool runs. The merino-nylon blend improves stretch and durability while taking advantage of the best features of merino wool.

This is a great option when you need a shirt that can stand up to long runs or multi-day use without frequent washings. The men’s and women’s versions come in a few neutral color options that are perfect for an active travel trip where you want to pack light and need a shirt that can work just as well on a hike or run as it does strolling the streets or at dinner. And those travel times when you need to dress up, the shirt can offer comfort and a pop of color beneath a collared shirt or blazer.

This performance doesn’t come cheap, and the shirt is a significant investment at $90, but its versatility and ability to be used in so many different settings and climates may make it one of the only t-shirts you need in your closet. From 100-mile ultramarathons to trans-Atlantic flights, this shirt will keep you dry and comfortable no matter what Mother Nature or a busy airport throws at you.

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Quick Drying Fabric The Black Diamond Rhythm T-Shirt.Photo: iRunFar/Eszter Horanyi