Replacement kits vary by listing but commonly include the brush roll and the bottom plate. Some kits instead or additionally list replacement pump components or roller brush belts as part of the accessory set.
These brush rolls are described as multi-surface: suitable for sealed hard floors (hardwood, tile, laminate, linoleum), area rugs, and some low-pile carpets. Several listings explicitly call out hard floors and area rugs or low-pile carpet.
Several listings recommend replacing the brush roll about every six months to maintain optimal cleaning performance.
Some stick-style and lightweight machine listings note a motorized (or more powerful motorized) brush roll in their product features. Check the product features list on the listing to confirm whether a motorized brush roll is included.