CFR > Title 33 - Navigation and Navigable Waters > CHAPTER I—COAST GUARD, DEPARTMENT OF HOMELAND SECURITY > SUBCHAPTER S—BOATING SAFETY (parts 173 to 188) > PART 181—MANUFACTURER REQUIREMENTS > SUBPART C—Identification of Boats (§181.21 to §181.35) > 181.21—Purpose, applicability and effective dates.