The short answer
Whisker's own Litter-Robot waste drawer liners fit the Litter-Robot 3 and 4 and hold 9 to 11 gallons. Third-party packs from ANWA, AWoHH and KONE state Litter-Robot compatibility and cost less per bag; their fit relies on the seller's statement.
Official liners
Whisker Litter-Robot liners come 25 to a pack. On the Litter-Robot 4, wrap the edges over the drawer rim.
Compatible bags
Other add-ons
The Litter-Robot 4 bundle we cover includes OdorTrap refills, liners, wipes and carbon filters. For the older Litter-Robot 3 there's Whisker’s LR3 ramp and LR3 carbon filters.
Products mentioned
Questions readers ask
Do generic bags fit the Litter-Robot 4?
Several third-party packs state they do; check the model list on the pack.
How many liners come in Whisker's pack?
25.