High quality Timbuk2 Pannier. Lays over the rear rack of bicycle, attaches with Velcro straps along the rack, as well as loops on either side side to the rear rack frame. All velcro to remove. Stays on tight though. Two pockets that are padded and pretty rain resistant. Comes with a detachablee shoulder strap. Overall a veryy sleek and functional pannier option. Will last a long time, in good condition, only minor signs of wear.