This is the Keela GEN 2 Jungle shirt, of which used similar techniques much like the old traditional shirt with a couple of extra additions. 

The KEELA shirt provides extra durability, stretch and far more comfortable with using a special mix of fabrics that regulates heat and extracts moisture and retain within the fabric itself.

Key features in a breakdown - 

• Quick drying, lightweight and durable.
• UV/VIS/IRR 
• No hook and loop! 
• no melt or drip
• Velcro loop IFF Panel on each upper arm. 
• IRR button cuffs 
• Inter-grated compass pocket 
• Two large chest pockets with IRR button closures 
• Extra long flat construction with scooped rear
• Front flap with covered button and YKK Zipper to aid ventilation. 
• Pre shaped sleeves
• Reinforced Elbows