Wear-tested and reviewed by: Julia Polloreno

This Rock ‘n’ Roll Marathon Series In-Training Tee appeals to the same sense of wonder and intrigue we felt as kids while playing with invisible ink. Only now, instead of ink, your hard-earned sweat is uncovering the secret message. How it works: as you perspire, hidden lettering begins to emerge. (No weird chemicals or harmful ingredients are used—the “sweat-activated” fabric is non-toxic and hypoallergenic).

I recently wear-tested the Rock ‘n’ Roll Marathon Series In-Training Shirt during an hour-long run. (A men’s t-shirt version is also available). Here are my five takeaways:

The sweat-activated technology really works.

Pre-workout, the tee has a clean design featuring a red and white Rock ‘n’ Roll Marathon Series logo across the front. About 20 minutes into my run, I noticed that my sweat was beginning to form letters across the chest and midsection of the tee. By the time I finished my run, you could see the “Run With Us” design clearly.

The tee was both functional and flattering.

I liked the v-neck cut at the front, forgiving fit (sizing runs a bit large, so consider sizing down if you like a tighter feel up top), and the silky-soft feel of the combed cotton/modal blend fabric. The dark blue tee color looks great against a variety of skin tones, and the logo pops in vibrant red.

The cool packaging is a fun bonus.

The tee arrived in the mail inside a sturdy tube that’s wrapped in Rock ‘n’ Roll branding. The inspiring imagery will remind you the goal at hand every time you look at it. Mine now sits on a gear shelf, repurposed as storage for my watches and cords.

There’s no special care required.

Just toss the tee in the wash and treat as you would any other piece of training apparel. After the dry cycle, the special graphics disappear. The shirt’s sweat-activated feature should last for dozens of washes.

Wearing the tank adds a motivational kick.

It doesn’t matter where it comes from—any motivational edge is useful. The bold logo across the front proudly proclaims you’re a Rock ‘n’ Roll runner in training (from 5K to Marathon), and it’s fun—and surprisingly gratifying—anticipating the “Run With Us” message. You’ll finish your workouts with visible proof of that “earned it” feeling.