Our bestselling 72-Hour T-Shirt is cut from a merino wool blend that’s naturally thermo-regulating, moisture-wicking, and odor-resistant. This “Tactical” version takes those properties and doubles down on durability, infusing the fabric with Spectra®—a fiber 15x stronger than steel, used in everything from body armor to performance sailing lines. That means the tee not only stays fresh after more than three days of nonstop wear but can also hold up to the most rigorous efforts.