Speaking strictly for using them as undershirts, they're 4 star. As exterior T-Shirts they'd probably get 3 stars. First, they shrink/run small. This doesn't bother me from an undershirt perspective because I don't want my undershirt's sleeve or tail to stick past my collared shirt anyway. The fabric is on the softer side and does breath reasonably well. But these ARE NOT the common "sport" or "under armor" style fabric. These certainly feel like cotton. In terms of thickness or what I think durability will be...they're fair. I've had thinner and cheaper feeling shirts, but they're not as thick as the Hanes Beefy series for example. All in all, I probably would not buy them again. Im not a strong believe in the whole X-Temp marketing and the "Beefy" line is clearly higher quality.