B7 - certified to ASTM A193 or ASME SA193
A heat-treated chromium - molybdenum steel that is widely used for medium to high temperature service. Minimum tensile strength is 125,000 psi and the maximum hardness is 321 HB (under 2-1/2" diameter)

B7M - certified to ASTM A193 or ASME SA193
Same chemistry as B7 above but with reduced strength and hardness. Generally used in environments where chloride or sulfides are present to provide improved corrosion resistance. Minimum tensile strength is 100,000 psi and the maximum hardness is 235 HB (under 2-1/2" diameter)

B16 - certified to ASTM A193 / ASME SA193
A heat-treated chromium - molybdenum - vanadium steel generally used for high temperature service (up to 1100°F). Has identical strength and hardness requirements as B7.

L7 - certified to ASTM A320 / ASME SA320
Similar chemical and physical characteristics as B7 but designed for use in low temperature service.

L43 - certified to ASTM A320 / ASME SA320
Similar strength characteristics as L7 and B7. Again designed for use in low temperature service.

A307 Grade 2 Low Carbon Steel
A special low carbon steel with controlled amounts of Phosphorus and Sulfur, and with a minimum tensile strength of 60,000 psi.

2H - certified to ASTM A194 or ASME SA194
The industry standard for use with B7 studs. Suitable for high temperature and high pressure service.

2HM - certified to ASTM A194 or ASME SA194
Generally used with B7M studs. Designed for use in a high temperature corrosive environment.

Grade 4 - certified to ASTM A194 or ASME SA194
Designed for use in conjunction with B16, L7 and L43 studs although they are sometimes used with B7. Suitable for a wide range of temperature and strength applications.

Grade 7 - certified to ASTM A194 or ASME SA194
Again used primarily with B16, L7, and L43 studs, this chromium - molybdenum steel is suitable for extreme sub-zero service temperatures.

B6 - certified to ASTM A193 / ASME SA193
Commonly referred to as 410 stainless this material has a minimum tensile strength of 110,000 psi.

B8 - certified to ASTM A193 / ASME SA193 or ASTM A320 / ASME SA320
This nonmagnetic material has good corrosion resistance for use in service temperatures of -325°F to 1500°F. This Chromium-Nickel (AISI 304) steel has minimum tensile strength of 75,000 psi.

B8 Class 2 - certified to ASTM A193 / ASME SA193
Same as B8 above but strain hardened to provide greater strength (up to 125,000 psi for diameters 3/4" and under).

B8M - certified to ASTM A193 / ASME SA193 or ASTM A320 / ASME SA320
Similar to B8 but with added Molybdenum for better corrosion resistance than B8 in most environments. This material (AISI 316) also has a minimum tensile strength of 75,000 psi.

B8M Class 2 - certified to ASTM A193 / ASME SA193
Same as B8M above but strain hardened to provide greater strength (up to 110,000 psi for diameters 3/4" and under).

18.8 Stainless Steel
Several grades of stainless including 302, 303, 304, and 305 are included in this generic classification. All have good basic strength and corrosion resistance.

316 Stainless Steel
Another generic stainless classification that has better corrosion resistance than 18.8 stainless steel in most environments. This material also maintains its strength at higher temperatures than 18.8.

Grade 8 - certified to ASTM A194 or ASME SA194
Designed for use with B8 and B8 Class 2 studs in corrosive environments over a wide temperature range.

Grade 8M - certified to ASTM A194 or ASME SA194
Designed for use with B8M and B8M Class 2 studs. Generally offer greater corrosion resistance in most environments than does Grade 8.

18.8 Stainless Steel
Designed for use with the 18.8 studs above, this classification includes several grades of steel including 302, 303, 304, and 305.

316 Stainless Steel
For use with 316 studs, this material offers greater corrosion resistance than 18.8 in most environments but is also more expensive due to the higher Nickel content and the addition of Molybdenum.