If its a jaunt to the beach or traipsing the Rails-to-Paths, the Gregory Trinity 18 Backpacking Backpack - Girl's is the Great size for a long day out for you and your stuff. Its offset zipper allows for wide panel access to the main compartment, which is large enough for a jacket or beach towel, while an interior mesh organizer with key clip, second padded compartment, removable discrete pocket, waistbelt pocket, and side mesh pocket keep Must haves organized. When you don't necessity it, the Trinity 18's waistbelt tucks away.