Plastic or fiber glass, good quality product. Easy to use. The Magician displays a clear plastic sheet in a decorative frame. The audience can examine this. Two playing cards or Visiting cards are now sandwiched in the frame with the clear glass between.
The magician pushes a pencil through the middle of the frame, making two holes in the cards. But when the cards are removed, the clear glass sheet is found to be entirely intact.
The pencil has magically penetrated through the solid glass sheet, without damaging it in any way! And everything can be examined by your spectators.