exhuast tips

i was looking to buy the dual tipped stainless steel exhuast tips for 90 bucks from fasttoys.net and i was wondering if you can just use the clamp that is already on the old tips or if you must have it welded to the pipe. i have seen these tips on many gps and was just making sure they will fit no prob on my car. im curious what anyone that has had these put on their car has to say. thx
heres the site for them http://fasttoys.net/shop/product_info.php?products_id=183&osCsid=4c0b0ca8b02b8866037f4fc613c99562