good place to look for info are crutchfield.com and sounddomain.com ... although crutchfield lists the front speakers as 4". ignore that. it is 5-1/4" (crutchfield says only 4" fit, but infinity audio says a 5-1/4" will fit). crutchfield has a help center too. what is annoying is most aftermarket speakers have a somewhat circular/symmetrical mounting points, the volvo has a more eliptical shape. nothing serious, but u just have to make new holes to screw the speakers in place. another thing u may wanna do is head to ur local shop and hear the speakers physically. but keep in mind what u hear in a room is gonna be diff in a car...diff shapes and all. also, some of these audio aftermarket companies have their own little pamphlets that r downloadable...like polk audio.