The h710i does not support 360mm radiator because there are no holes on its back panel like other models do have (h700i/h730i/h750i). You can still use your existing 240mm radiator but you will need two fans instead one fan as there are two 120mm fans on top side panel (see picture below). You can also use 2x120mm fan(s) if you want bigger cooler area by using 2x120mm fan(s).