Soft Panniers........used them for years They come in different shapes, sizes, styles and materials to suit different styles of bike, be it sports bikes or cruisers. They also vary in cost, some cheap and cheerful, some bl**dy expensive! BUT they are not generally waterproof and are normally supplied with plastic covers. Main thing to be wary of is burning/melting them on the exhaust and/or silencer by buying some that are too large for your bike (it does happen). Also don't overload them and try to even out anything you put in them. Fitting them: They are held in place by a strap with velcro that goes under the seat and (usually) 2 straps that fit over the pillion seat again by velcro which are adjustable to some degree. the bottoms of them are held in place by a strap that either fits to the pillion footpeg mount (might need bungees as well?) or round the twin rear shox (if you have got them). It is I believe possible to use padlocks on the zips of some to stop theft, but probably wiser to take them with you when you leave the bike. They are easy to attach and to remove should you want to, as they are held in place by velcro straps, you will though also have to remove the seat to get at the strap underneath it.