16 C.F.R. § 1203.10 Selecting the test headform.
Title 16 - Commercial Practices
A helmet shall be tested on the smallest of the headforms appropriate for the helmet sample. A headform size is appropriate for a helmet if all of the helmet's sizing pads are partially compressed when the helmet is equipped with its thickest sizing pads and positioned correctly on the reference headform.
Title 16: Commercial Practices
PART 1203—SAFETY STANDARD FOR BICYCLE HELMETS
Subpart A—The Standard
§ 1203.10 Selecting the test headform.