Capacity
Volume: 1 litre
Can fit a spare inner tube, tyre levers, patch kit, etc.
Easy assembly / dismantling
Easily attaches in 2 spots (saddle and seat post) with rip-tab bands.
Easy opening / closing
Zipped closure for easy access to your belongings, even on the saddle.
Robustness
Very robust materials for a longer lifespan.
Compatibility
Specifically placed to accommodate a light.