For Sale: Gravel Travel Modular Backpack – Black (Discontinued/Sold Out) Up for sale is a pre-owned Gravel Travel Modular Backpack in black. This item is discontinued and sold out, making it a great find for travel enthusiasts and collectors alike. The backpack shows normal signs of use but remains in good functional condition. It's ideal for travel with a sleek, modular design that allows for versatility and efficient packing. * Approximate Dimensions: 21" x 15" * Please see photos for condition and details.