Bushwhacker Carson Black - Bicycle Expandable Seat Wedge w/Reflective Trim & Light Clip Attachment - Cycling Under Seat Bag Bike Rear Pack Saddle Bag Frame Front Accessories Attaches under your seat with two secure straps. Expands from a hideaway pocket and adjusts to fit with compression straps. A stiff inner shell maintains its shape. Reflective trim increases visibility. Constructed with durable 600 denier polyester. Dimensions: 6.5" L x 5" W x 5" H Expanded: 6.5" L x 5" W x 7.5" H