When combining accessories and adapters, the low load capacity / payload is relevant.
Bikepack X Waterproof
Contour Saddle Adapter · black
Large bikepacking saddle bag – simply to click on saddle
Large waterproof bikepacking saddle bag that can be mounted and removed in a flash without needing to fasten countless straps. Simply click the bag onto the Contour Saddle Adapter and fix the Velcro loop around the seatpost, the bag sits securely without swinging. The volume can be varied by the practical roll closure between 8 and 10L, so that the contents in the padded main compartment are protected from slipping. A rain jacket or other things that should be quickly accessible can be stowed outside under the luggage spider. The combination of lamp holder and reflector provides better visibility.
The two point attachment paired with the stable internal structure doubles the load capacity for Bikepack X bags of up to 4kg max.
These bags were developed for bikes without carrier. They provide lots of space as well as good protection against dirt and water.