The Big Step tamper base was a result of the desire for a base with the highest possible tolerance in size for VST baskets. It's called the Big Step because the design of the larger diameter "stepped edge" measures at 58.60mm (-0.02). What this does is to enable a maximum surface area of extraction, including the very edge of coffee grind that sometimes can be pinched when using such a large (or incorrectly) sized base.
This base is manufactured in Australia from a super hardened (minimum 40 Rockwell standard) 630 grade stainless steel. For Pullman's fans, the Big Step retains the solid feeling of a regular barista base, and is designed with those in mind who perform a standard tamping technique (including the "puck polish" final step). The sharpened bottom of the Big Step allows perfect coverage of the inside of the VST baskets, which also prohibits air pockets at the very bottom of the baskets once the coffee is packed in. There is also less room for error by the barista as the base will not go into the basket unless a perfect level tamp is applied.