For 2-hour fire-rated pipe insulation, the most commonly used material is mineral wool or rock wool insulation. Mineral wool insulation provides excellent fire resistance and can maintain its integrity for up to 2 hour fire rated pipe insulation.

Some key features of mineral wool pipe insulation for 2-hour fire rating:

- Made from naturally occurring volcanic rock and slag
- Provides high temperature resistance, up to 1200°F (650°C)
- Noncombustible and does not contribute fuel to a fire
- Maintains structural integrity and insulating properties during a fire
- Meets ASTM E119 and UL 263 standards for 2-hour fire resistance
- Commonly available in pipe section or roll form for easy installation around piping

Other materials like calcium silicate or perlite-based insulations may also be used for 2-hour fire-rated pipe insulation, but mineral wool is one of the most common and widely-used options. The specific product selection depends on the pipe size, operating temperature, and local building code requirements.