It is made from anodized aluminium with a stainless steel base.
58,4 mm diameter, fits in most VST baskets. Because of the precise diameter, it is not a one size fits all.
Distribute the coffee even in your (VST) filter basket. Tamp your coffee until you feel resistance from your coffee. Harder is not always better, nor is faster. Make sure to be straight, rather than being really strong. When you pull out too fast, the coffee may get into a vacuum, so be cautious when pulling out of the filter basket.