The ORTLIEB Seat-Pack M is compact and spacious at the same time. Offering a payload of 11 liters, the waterproof seat bag offers a lot of stowage space for sizeable items that are not so heavy such as clothing and personal care items. The inside and bottom of the bag are stiffened, which ensures stability even in bumpy terrain. Thanks to the roll closure, adjustable straps and an additional compression valve, you can reduce your loaded Seat-Pack to an extremely compact size.
Outfitted with highly adhesive Velcro straps, the waterproof Seat-Pack M easily attaches to your bicycle saddle rails and seatpost. And given that you only need 6 cm of available space on your seatpost, the Seat-Pack is also ideal for smaller frames, full-suspension MTBs and bikes with dropper seatposts. The attachment to the saddle rails reliably holds the Seat-Pack M in the right position, essentially turning it into an effective fender.
+ Reinforced fabric at points of contact to the seat
+loops for LEDs positioned for various rolled-up states
+ vertical daisy chain for rear light
You want to know how to attach the fixing strap,Please see this YouTube Video .