This National Safety base layer shirt features temperature-regulating technology, which keeps you cool on warm days and warm on cold days. Translation - total comfort in all seasons. The fabric also provides moisture-wicking and anti-microbial properties so you can stay dry and fresh even on the most intense work days. This shirt can actually lower perspiration by as much as 34 percent! This long-sleeve base layer has an ARC rating of 3.6 cal/cm2 and is NFPA 70E compliant. Lastly, it's made right here in the USA!