ASTM A240 is a specification for stainless steel sheet, plate, and strip. It is often used in the construction of pressure vessels and other applications that involve exposure to corrosive environments. The specification covers the standard requirements for materials and dimensional tolerances, as well as the mechanical properties, testing, and inspection requirements for these materials.

The standard includes several grades of stainless steel, including:

• 304 and 304L: These are the most common grades of stainless steel, and are widely used in the food and beverage industry, as well as in architectural and other applications where corrosion resistance is important.

• 316 and 316L: These grades are also widely used in the same applications as 304 and 304L, but offer improved resistance to corrosion in environments that contain chlorides, such as saltwater.

• 321: This grade of stainless steel is similar to 304 and 304L, but offers improved resistance to intergranular corrosion and high-temperature strength.

• 904L: This grade of stainless steel is highly resistant to corrosion and is often used in chemical processing and marine applications.

All of these grades are available in the form of sheet, plate, and strip, and have specific mechanical properties, testing requirements and dimensional tolerance accordingly, it will be clearly outlined in ASTM A240.

It is important to note that ASTM A240 specification only covers the requirements for stainless steel sheet, plate, and strip, and do not cover other forms such as bar, rod, or tubing, for those the corresponding standard will be different.