They standard ones don't come in cages...
Undo the two screws on the centre console, use a spatula to prise the trim off. You'll then see 4 screws, 2 on either side of the headunit, undo these and it'll come straight out.
Remember to take off these brackets from the original radio onto the new one you're putting in.
Mine was a Sony, but came with the optional upgraded Clarion speakers.