The osprey kestrel 28l daysack is the most compact of the kestrel range and is ideal for daytrips or lightweight overnight hikes the kestrel 28l takes advantage of all of the technical features exhibited in the larger models including the airscape back system which is highly breathable and ventilated for maximum cooling during more tougher activity the straightjacket compression system helps to balance regulate and contain pack weight allowing for freer range of movement with 28l of storag