Diver's Lung Tester — Prank Toy

Think you've got diver's lungs? Prove it — or prank someone who thinks they do.

The Diver's Lung Tester looks like a simple blow-challenge toy: put your lips on the mouthpiece, blow, and try to spin the internal wheel as fast as you can. But there's a secret second function hiding inside.

How it actually works:
Inside the body are two separate air channels:

• Main hole (the obvious one): blowing straight into this sends air into the internal flour pocket, pushing flour out through the two posts that support the wheel axle — right into whoever's face is closest. This is the prank function.
• Second hole (the trick): plug the main hole with your tongue while blowing, and the air redirects into this channel instead, spinning the wheel cleanly with zero mess.

Assembly:

1. Fill the body's flour pocket with flour (a funnel or small spoon works well).
2. Screw the cap on to seal it.
3. Slide the axle through the first mounting hole on the body.
4. Push the axle through the center of the wheel.
5. Continue the axle through into the second mounting hole on the other side to hold everything in place.
6. Done — 4 pieces, no glue needed.

How to prank someone with it:

1. Demo it to your friend by plugging the main hole with your tongue and blowing into the second hole — the wheel spins, no mess, looks totally harmless.
2. Turn it into a challenge: "Bet you can't spin it faster than me!"
3. Hand it over. Most people instinctively blow straight into the main hole without plugging anything — and get a face full of flour instead of a spinning wheel.

Features:

• 4-piece assembly: body (contains both air channels + flour pocket), wheel, axle, and removable screw-on cap
• Cap unscrews for easy flour refills
• No supports needed on most parts

• Compact, fast print, great gag gift or party trick

  Video on how it works