Effect: A long balloon is inflated inside a square tube, and "penetrated" with four spikes and a metal blade, without bursting the balloon.  In the instructions it mentions a valve which nothing more than a tiny ring with which to place on the nozzle of a balloon to hold the air in, this is not present and a knot just does as well.  Balloons not supplied.  Includes 3 pages of illustrated instructions.

Condition very fine.