Shadows used in the components are derived from a 6-step scale. Shadows

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Shadow tokens

Shadow tokens can be accessed using CSS variables. You can use these tokens to style your custom components, ensuring they are consistent with the rest of your theme. 
/* Inset shadow */
var(--shadow-1);

/* Shadows for variant="classic" panels, like Card */
var(--shadow-2);
var(--shadow-3);

/* Shadows for smaller overlay panels, like Hover Card and Popover */
var(--shadow-4);
var(--shadow-5);

/* Shadows for larger overlay panels, like Dialog */
var(--shadow-6);