We have a 1998 Rialta and put in two new coach batteries this summer. If you go to Baldy's Rialta website, it talks about how tight the fit is for two batteries. We ended up at Walmart and purchased 2 deep cycle marine batteries. One is the size recommended in the owner's manual, the second was just slightly smaller. We wired as recommended. They worked great on our 5 wk. trip cross country. I will try to post actual sizes as soon as I can. 18" of snow today so I can't get into the RV!