Extensions are three types: CFX 1,3,5.

The overall influence of the extension on the measuring uncertainty is mainly determined by three factors: weight, thermal expansion and static stiffness.

CFX Extension  types are equal in weight and thermal expansion.  All perform better than aluminum and titanium. 

A CFX 1 extension will have the most deflection and will also be the least expensive. 

CFX 1 is used with Contura, Duramax, O-Inspect, and Spectrum machines. 

CFX 3 is used with Prismo, Prismo Fortis, and Accura machines.

CFX 5 is used with Xenos, Micura, Prismo Ultra, and Prismo Verity.