they're the rolies. you have to order wolfman's saddlebag mount for them to work like I have them in the picture. awesome system though! http://wolfmanluggage.com/index.cfm?fuseaction=product.display&product_id=122 I have a large on top and med on the sides but they fit snug. it's recommended to use either 3 med or a med/small combo but if you think you'll carry a lot, go with the large on top. comes out to about 29L total capacity.