import { Box, handleBreakpoints } from '@mui/system'; import { createTheme, ThemeProvider } from '@mui/material/styles'; const customTheme = createTheme({ unstable_sxConfig: { size: { style: (props) => { const { size, theme } = props; const styleFromPropValue = (propValueFinal) => { const value = theme.spacing(propValueFinal); return { width: value, height: value, }; }; // Adding support for the breakpoints syntax return handleBreakpoints(props, size, styleFromPropValue); }, }, }, }); export default function ExtendTheSxProp() { return ( ); }