I have checked out all of those and they aren't bad, but they are not as secure as I would like. They are good for most situations though. They keep honest people honest. I have an Ortlieb TourBox now that provides about as much security as one of those listed but it's not a top rack box. If I were going to get a plastic top rack I think I would go for the Gerda Bike Touring safe. It also has a cooling (styrofoam) insert designed to fit inside which converts it into a cooler. Cool eh! No, I need something that is gonna keep someone really dishonest occupied for a while if they want to rip me off.Here is a link to the Ortlieb that I have and the one for the Gerda.

http://clearance.bscbikes.com.au/ort...x-pannier-bag/

http://www.bikester.co.uk/bicycle-eq...ell-cases.html