This is the HFD Duty Nomex IIIA shirt.  Its made of 4.5 oz 100% Nomex IIIA plain weave fabric. Its Certified to meet NFPA 1975 Regulations. It also includes:  

• a panel front with hidden snap closure for easy access
• two mitered breast pockets with hook and loop closure
• a left pocket flap that  includes a pencil/pen slot
• and a fuse banded dress collar and cuffs
• Sleeve Patch Included With Purchase.