After removing the OEM tweeter you get this little tweeter bracket. It is very small,
So i had to alter it to fit Focal K2,I think most Aftermarket Tweeter will be Bigger then OEM, here the step it took

http://i261.photobucket.com/albums/ii73/Nalaar/t1.jpg

Cut off the clip on the braket that held the OEm tweeter, with a Knife
http://i261.photobucket.com/albums/ii73/Nalaar/t2.jpg

Place new Tweeter into the Tweeter pod
http://i261.photobucket.com/albums/ii73/Nalaar/t3.jpg

Put you modifed Braket on and screw them in. Done
http://i261.photobucket.com/albums/ii73/Nalaar/t4.jpg

Last thing, If you dont mind destorying your OEM Tweeter, Break The Harness off OEM Junk and you can get a pair of nice wiring harness for you Aftermarket Tweeters.
http://i261.photobucket.com/albums/ii73/Nalaar/t5.jpg