Most helmets have little cut out behind the lining, mine didn't but the speakers are so slim it doesn't matter. I've got a similar one to user650 about £20-£25 on fleabay with a big dial on the outside to adjust the volume, I wear an ear plug and it's plenty loud enough at normal legal speeds, also answers the call automatically after so many rings, great for Sat Nav too. I'm a Blood Biker so I use it a lot with Sat Nav and phone.