Bought this obviously for the Canon EOS 450D. You do not need to buy an extra Battery Pack (Canon LP-E5) as this unit will function with just one but can take two, extending your shooting capabillity. What I didn't know was that it also comes with an extra battery tray which enables you to use 6 AA (Walkman tm) Battery's great if you loose power or cannot get to a power point. Something that happened to me at the Volcano in St Lucia, sure enough the gift shop sold AA's so all was not lost. As for build and quality, similar to the EOS and once easily fitted looks like one unit. It does add quite a bit of weight to the Camera but this is to be expected, though Canon have thought of this and there is a hand strap available . A nice feature is the unit has an extra set of zoom buttons, AV +/- buttons, a scroll wheel and also an extra shutter release button, great when using the camera in the vertical position as this enables control over them using your right thumb and forefinger. These can be switched on/off with....er the on/off button on the unit. In summary a great piece of kit, with the added usabillity of over the counter battery's widely available across the develpoed and not so developed World.