Normally, I am an aluminium guy, but waterbottle cages are one are where I believe steel is real. Accept no substitutes, King Cages in stanless steel for $15 each are the best thing going. They last forever, don't mark your bottles, and look pretty. For the weight weenies, you can get the TI version for $60 that weights 28 grams instead of 48 grams for stainless. Given that the lightest carbon cages are 15-20 grams and break at the slightest provacation, while costing major $, the TI is a far cheaper alternative.