Sorry to the previous reviewer that this shirt wasn't up to specs.  The standard 6.75 oz short sleeve t shirt is bullet proof for any type of work however it is unbearable in summer.  I'm talking August in the south with a shirt back that's soaked.  So carhartt made a heavy duty wick dry shirt (compare this to normal workout wick dry shirts and you'll see it's a lot more durable).  Granted you probably can't crawl thru semi truck engines without shredding it but it will help control your body heat. So it's a trade off, wear the heavy shirt in August and risk heat stroke or this one and sacrifice some durability.