This is the espresso machine basket developed by VST.
Each basket has been designed and created in such a way that it guarantees a size, distribution and shape of holes perfectly suited to extract the chosen amount of coffee.
In essence, this means that you can now grind finely enough to properly extract your dose of coffee, while still maintaining a desirable flow rate and brew time of approximately 25-30 seconds.
There is more information here.
18g basket: Height (mm) 24.2, Outside diameter (mm) 60.0
20g basket: Height (mm) 26.0, Outside diameter (mm) 60.0
22g basket: Height (mm) 28.0, Outside diameter (mm) 60.0
To check if a VST basket is compatible with your espresso machine check here.
Wide outlet angle prevents clogging, anti-wear design ensures uniform extraction performance for life of product
All holes are measured for circularity, placement, square area and blocked holes
Designed to fit with most 60mm Portafilters
Recommended Tamper: 58.2-58.4mm diameter, flat face