This is an attachment for the LGB track cleaning block that can convert it into a track cleaning car. Wheels and couplers (Kadee 8/930s) go onto to the attachments, then attachment is slipped onto the posts of the cleaning block. (It can split apart, there are clips on the side holding it together - Push the sides in and pull). This works well when tacked onto a train, though the wheels do come out slightly too high. The flanges do still work, and it tracks well as long as it's on the end of the train. This is a very long unit, and will not clean the outer rails of an R1 curve. It will run through it though...

Tip: Use metal wheels; they'll bend the plastic down enough to allow the wheels to make contact