Designed specifically for bikes with dropper posts. The Dropperpack is simple to attach and waterproof, shrugging off everything mother nature can throw at you. A solid option if you're new to seat packs. Plus, Oceanweave Ocean-X multi-layer fabric is made from reclaimed and recycled fishnets to help protect the world's oceans and marine life. Mounting: Heavy-duty seat rail buckle and straps; pull up to tighten. Materials: - Waterproof Oceanweave(R) Ocean-X multi-layer laminated material made from reclaimed and recycled fishnets. - Hydracore(R) panels provide an exceptional IPX4 waterproof rating - Buckles are made from reprocessed polyamide and reclaimed textiles (clothing). Compatibility: Most bike seats - Specs: Dimensions: 25 x 14 x 12cm (9.8 x 5.5 x 4.7in.) - Weight: 133g (0.29 lb.) - Volume: Capacity: 3.6L Features: - The perfect balance of function and lightweight. - Waterproof outer fabric sheds dirt and water easily and is incredibly durable. - Roll-top closure, similar to drybags. - Reliable strap and buckle mounting system. - Lower spine for increased stability. - Back strap allows for overloading. - Reflective 3M(R) logos on two sides increase visibility at night.