ACT Trail 22 SL Hiking Backpack Black. These full-contact hiking packs have already won over many fans, due to their optimum weight bearing ability and load control. The flexible DelrinÂ® Aircontact back system construction fits any back shape comfortably. The compact 2 SL model is a real gem for women â?? not only on day hikes, but also during city trips since the lightweight mesh hip fins can easily be stowed away.