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Aluminum conducts heat incredibly well but lacks adequate heat retention
Stainless Steel retains heat for an incredibly long time but does a poor job of distributing it evenly
By layering the aluminum between the stainless you achieve a pan that holds heat and distributes it from the cook surface to the top of the rim.
Two type of stainless Kovea takes this a step further with this kit, by utilizing 18/10 stainless for the inner layer, and 430 Series for the outer layer you get improved stick resistance and durability on the inside, and a corrosive resistant magnetic exterior which allows use on all cook surfaces - glass, flame, or induction.