A Base Layer can be worn all year round, insulating in cold conditions and  then in hot conditions managing moisture & also prevent skin sticking to linings.  EDZ offer two types of Base Layers:

All Season Base Layer is a performance polyester base layer which can be worn over a wide spectrum of temperatures from hot to cold. This is fast drying and if rinsed out at night will be dry by morning.

    
Merino Base Layer is a 100% wool base layer with the natural temperature regulating properties of wool.

Which Base Layer to choose?

The All Season base layer works across a wide range of temperatures & and would be the first choice in warmer conditions wheras the Merino will give a higher level of insulation when it is cold.