Single compartment with a wide Velcro fastening on the flap. The webbing straps fit through the rails underneath the bike saddle and clips round the front of the bag with side release buckles and a slider for easy adjustment. The double sided Velcro attaches round the seat tube to keep the bag in place.
We recommend that you put the inner tube in first so it sits next to the seat post. Please ensure that your saddle bag straps are fitted through the saddle rails, wrapped round the bag and tightened as much as they can be so it doesn't move about when you are riding.
The bag is big enough to hold an inner tube, tyre levers and tools as well as any other small items you might need to carry with you.