If you do need more info on this subject,check out the $49.99 thread I just started.I have used the carr product and seen the other two.None of them are bad.
I have also used the B&B parts and can heartily reccomend them,especially the mount,which is simple,as short as possible (with the carb and muffler on the back the Ryobi is already a long package)cheap,and bulletproof.See.
WWW.bennettbuilt.com