It's a plastic tube in the vent hole of the floor tom. You can see him place the tube in his mouth at 2:10, he's simply blowing air into the drum. Benny Greb did the same thing at the Chicago Drum show except he actually got on the floor and blew right into the drum.
From 2:11 In this video, how David is playing bending tune with just playing one floor tom?
I'd say just measure the vent then take a trip to your hardware store, plenty of nylon/plastic tubing there. Nothing drum-specific about it, just experimentation.Thanks for letting me know hoc information! Do you know how I install it to the vent hole? Is the tube specially made for drum set?