Tubemate is wonderfull application to download any quality of video. It is smaller application and easily operate on any android. It is easliy available on google. Its look is awesome. At notifiaction bar there is boxes are appear which shows how much downloading is held.
It has feature that it is capable to download any video that is unavailable to download on youtube. Its downloading speed is high. I also use this application from a very long time. It is also download that videos which is high quality and not easily available.