That is what I'm using !
@ FML very nice tunnel gun :yh: a couple years ago I made a simmilar device but no motor or battery it worked on tap tap and so it was much smaller and slipped on and off the end of a pen laser. in place of the motor was a skinny 1" long coil spring if you get the right length it sets up a harmonic when you tap it lightly and the tunnel can take on some wonderfull shapes, BTW they are never a true round shape some time they go through round but they are alwaws moving and changing there shape... I have one mirror right now that dose that and it is on a motor shaft, very cool effect I will try to get videos.