This Quick Release model comes with a mount you install below your seat, for a more solid setup. Note! Do not mount on a saddle with carbon rails, on a carbon seatpost, a shock absorbing seatpost, or a dropper post. The first extra image shows the manufacturer's specification for what is required of your seat. - Waterproof material and welded seams - Adjustable volume: 8 - 13 liters - Velcro tab closure to the saddle post - PS21R material: fully waterproof, welded seams - Bungee cord on top for overpacking - Four high quality 3M reflectors - Place for a led light - 5 year guarantee - Made in Germany [Mounting instructions](https://www.ortlieb.com/media/downloads/anleitung/seat-pack_qr.pdf) (.pdf file).