The difference between Swiss Diamond’s classic series and HD Pro is that HD Pro features a stainless steel exterior and a waffle-style interior finish. Chefs have said that the stainless steel exterior works to optimize “the flip” – the strategic wrist movement cooks use to toss food in the pan – while the handles on the classic series are designed more ergonomically. BOTH the Swiss Diamond classic series and HD Pro are made in Switzerland and conduct heat evenly. If you cook on a gas stove, you may notice that the stainless steel base and sides may become discolored over time; however, this does not affect performance. Unlike the classic series, the stainless steel base requires a fair amount of elbow grease when cleaning to keep the cookware in pristine condition.