Premium MTB jersey, manufactured to really high standards using quality materials.
Lightweight, breathable, with a nice little zippable pocket on the bottom right hand side (credit card / emergency money etc) and a lens wipe too. Size wise, they run fairly true to size, but you may want to size up if you're on the cusp or prefer a looser fit. In the photo below I'm wearing a L, 6"3" (191 cm / 80KG), I'd definitely size up for armour. Arm length is excellent.
A combination of two materials: DryFast on the sleeves, side and chest and the back is constructed of a mesh fabric, designed to increase airflow, especially when using a backpack.