CFR
- Title 1 - General Provisions
- Title 2 - Grants and Agreements
- Title 3 - The President
- Title 4 - Accounts
- Title 5 - Administrative Personnel
- Title 6 - Domestic Security
- Title 7 - Agriculture
- Title 8 - Aliens and Nationality
- Title 9 - Animals and Animal Products
- Title 10 - Energy
- Title 11 - Federal Elections
- Title 12 - Banks and Banking
- Title 13 - Business Credit and Assistance
- Title 14 - Aeronautics and Space
- Title 15 - Commerce and Foreign Trade
- Title 16 - Commercial Practices
- Title 17 - Commodity and Securities Exchanges
- Title 18 - Conservation of Power and Water Resources
- Title 19 - Customs Duties
- Title 20 - Employees' Benefits
- Title 21 - Food and Drugs
- Title 22 - Foreign Relations
- Title 23 - Highways
- Title 24 - Housing and Urban Development
- Title 25 - Indians
- Title 26 - Internal Revenue
- Title 27 - Alcohol, Tobacco Products and Firearms
- Title 28 - Judicial Administration
- Title 29 - Labor
- Title 30 - Mineral Resources
- Title 31 - Money and Finance: Treasury
- Title 32 - National Defense
- Title 33 - Navigation and Navigable Waters
- Title 34 - Education
- Title 35 - Panama Canal
- Title 36 - Parks, Forests, and Public Property
- Title 37 - Patents, Trademarks, and Copyrights
- Title 38 - Pensions, Bonuses, and Veterans' Relief
- Title 39 - Postal Service
- Title 40 - Protection of Environment
- Title 41 - Public Contracts and Property Management
- Title 42 - Public Health
- Title 43 - Public Lands: Interior
- Title 44 - Emergency Management and Assistance
- Title 45 - Public Welfare
- Title 46 - Shipping
- Title 47 - Telecommunication
- Title 48 - Federal Acquisition Regulations System
- Title 49 - Transportation
- Title 50 - Wildlife and Fisheries
51.2091—Thickness.
Thickness means the greatest dimension between the two semi-flat surfaces of the shell measured at right angles to a plane extending between the seams of the shell.
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