5150 Xtreme Duty Cylinder Sleeves, also known as cylinder liners, are centrifugally cast, ductile iron cylinder sleeves. 

Benefits of Engine Sleeving Include:

• Increased Bore Size: Sleeving your engine gives the opportunity to increase bore size for higher displacement and increased engine capacity, resulting in more power and more torque
  - Increased Strength: Iron sleeves are stronger than alusil when subjected to high power, high stress applications, making the cylinder wall much less likely to crack under high performance conditions
  - Custom Cylinder Wall Thickness: With the ability to install a thicker cylinder wall, prepare your engine for high performance modifications, including high boost, turbo applications
  - Improved Heat Dissipation: By transferring heat more quickly and efficiently, sleeved engines are able to better withstand the higher temperatures associated with high performance applications
  - Improved Engine Longevity: By reinforcing critical areas and transferring heat quickly and efficiently, the risk of catastrophic engine failures under high stress applications is greatly reduced
  - Compatibility with Performance Modifications: sleeved blocks are better equipped to handle a wide range of high performance modifications such as high compression pistons, forced induction systems, and aggressive cam profiles.

Please note that sleeving an engine block is a complex and precise process that requires the expertise of an experienced machine shop or engine builder.

It's crucial to consult with professionals who are knowledgeable about BMW engine blocks and high-performance engine building to ensure that sleeving is the right choice for your specific goals and requirements.