I fitted a FMF 4.1 Titanium to my 570, fitment was easy, super light, about 100mm shorter then standard, came with 94db insert and spark arrestor insert, I purchased it from Riders Discount in the US via eBay, was delivered to my door for $358au
has a nice note to it even with the 94db insert fitted, it may be just me but the bike seems to run a bit cooler, so I guess the exhaust flow has increased.
I am very happy with it so far and would highly recommend it over a Akro, had an Akro on my last Berg and hated the Carbon brackets, they rub the pipe and are expensive to buy if you brake them
Hope this helps
Tim
P.S FMF also comes in blue