I have two rockets my 2005 I have owned since new and any time I need a battery(every four years) I hop skip and jump down to wallyworld and get one never had a problem in all these years.
somebody has to say it " fully charged one" seriously thou the higher cranking amp one you can afford that is the correct dimensions and consider replacing the pos and neg cables on bike with heavier ones to help with cold starting, it makes a huge difference