Minoura Gamoh KCL-1R Heavy Duty Rear Bike Rack - Durable Bicycle Cargo Carrier for Touring, Commuting & Cycling Adventures - Ideal for Urban Rides, Long-Distance Travel & Outdoor Exploration

This is a very stout rear rack. I have no doubt this will be able to carry anything I can fit in it. It's also rather larger, and heavy too. (Let's be honest though, if you're worried about weight, why do you want a rack to carry things on your bike in the first place?) I believe the dimensions of the bottom are close to 12"x17". Sure it's a little pricey, but the quality is excellent and it comes with more than enough mounting hardware. They include both M5 and M6 screws (depending on what your frame has). Overall, I'm extremely happy with this rack. It looks great on my bike, and I'm sure it will last as long, if not longer, than my bike.