The v4 is basically the screen and chip from the v3 in the body of the v2. Many people found the v3 design a huge fail. One important thing to note is that the v3 corrected the lack of ability to remove the top ring from around the connector. This is not the case in the v4. It seems they just put the guts of a v3 into the housing of the v2 thus taking a step backwards in regard to the top cap but a massive step forward in public acceptance of the aesthetic of the device.