The Franke composite sinks are really good, I've installed a fair few of them and so far haven't had any call backs. They don't do many sizes in the composite undermount though, just looked myself and the biggest single bowl is 540mm wide. If you want something bigger you'll have to go stainless. Also worth noting, I've recently just installed a black composite looking Franke undermount sink, only it was more plastic, to look at you wouldnt instantly notice, but if buying online unless you check you could end up with the wrong product.