floating-ui react-dom-interactions how to set floating element width same as reference width

In my react app I am trying to build a dropdown menu with floating-ui/react-dom-interactions (formerly knowns as react-popper). Here is a codesandbox link to a demo of my component. Here is a output of the current state of the app.

I want to set the floating element width same as reference element. I have tried to follow this approach from documentation but didn't get the desired output. How can I set the floating element width same as reference element.

And the last solution with size key , as defined in the package

const { x, y, reference, floating, strategy, context } = useFloating({
    placement,
    open,
    middleware: [
      offset(4),
      size({
        apply({ rects, elements }) {
          Object.assign(elements.floating.style, {
            width: `${rects.reference.width}px`
          });
        }
      }),
      flip(),
      shift({ padding: 5 })
    ],
    onOpenChange: setOpen,
    whileElementsMounted: autoUpdate
  });

Check sandbox - https://codesandbox.io/s/angry-marco-4yhuer?file=/src/SecondaryCategoryItems.jsx