airbag-compatible backpack with 30 litres of storage space. how big does a rucksack for mountain adventures have to be? 30 litres is the perfect choice - big enough to fit skins and more for a small tour, but small enough so it doesn't bother you while riding. the evoc line r.a.s. 30l is exactly this size, comes with numerous features, pockets and extras, has a back protector, an ergonomic fit and is compatible with mammut's r.a.s. airbag system.