Undertunic's are in there kind figuratively hard to confirm but high-medieval sources show that shirts were worn under the upper wash. Its also applies to the early middle ages because shirt is out of linen for funerals and other vestments are assignable (in the grave of balladoole, isle of man). The Vikings like to ware there shirts close to the body while the slaves were dressed rather in baggy vestments. It was important for the vikings that one could see all the layers of clothing when the complete set was worn. The fine fabric made the wearing of the over tunic a lot more conformable and In the summer its a good alternative for the wool.
Size Chart :
Designed in Germany by Burgschneider