Choke Tube Hazard Tester

Test whether or not an object is small enough for your child to choke on.

Directions: Place the object without compressing it inside the cylinder. If the object fits entirely within the cylinder, it FAILS the US Consumer Product Safety Commission test and MAY POSE A CHOKING HAZARD TO CHILDREN UNDER 3 YEARS OF AGE.

Where the (Inner) Dimensions Came from :
http://childsafetycentral.com/toy-choking-hazards.html

Another good site with some more detailed info:
http://babygooroo.com/2012/08/10-most-common-choking-hazards/