U.S. Toy regulation is defined by the ASTM 963-11:
Use a “choking tube” to determine whether a particular toy will pass/fail the rule.
– Toys meant for children under 3 years cannot have any part that fits in the tube entirely.
– If a toy or toy part does fit inside the tube, and is meant for children 3-6 years, then the toy must be market w/ a small parts warning.
– If a toy or toy part does fit inside the tube, and is meant for children 6+, then the toy is not required to have a small parts warning (though still recommended).