Here are your hints on how to use the inner layer present in most Spidi Adventure jackets: this is the Step-In Clothing system.
from +15°C to +35°C
The motorcyclist only wears the external shell, which is the most resistant in case of crash, and also contains CE protectors and possibly Chest or/and Back protectors as well. Once the 25°C are reached, mesh fabrics and vents start to become essential in order to allow air circulation and dissipate humidity.
Chilly to mild temperatures
from +5°C to +15°C and rain
External shell is worn coupled with H2OUT liner attached inside. H2OUT membrane is waterproof, breathable and windproof and increases resistance against bad weather conditions and chilly airstreams. On some Spidi jackets, this H2OUT liner is wearable as a stand-alone jacket for off the bike use, much like a K-Way.
from -5°C to +10°C
It becomes necessary to wear an insulating liner underneath the H2OUT. These liners keep the body warm while humidity is let go outside and are generally wadded and quilted and must also be comfortable and light. They may also be partly made by aluminium threading able to further enhance the insulation power by reflecting heating back towards the body.
More at http://www.spidi.com/eu/eu_en/news