The Sak Genuine Leather Convertible Backpack, Crossbody 。The Sak Ventura convertible leather backpack in black in excellent used condition. The Sak Ventura Flap Over Backpack is a black backpack made from rugged leather with studded silver-toned hardware and dark contrast stitching. It has a front flap that secures with a snap and reveals a front flip pocket and zip pocket. The interior has a back wall slip pocket, zipper pocket, and two front wall multi-functional pockets. The Sak Ventura Flap Over Backpack is a convertible backpack that can also be worn as a crossbody.