Every machine requires a different kind of Steady rest.  One should consider the following factors

1. Application
2. Size
3. Clamping Range
4. Working area

Based on the requirements or restrictions you should be able to choose the right model from the table below.

Steady rest applications	If the work area on the machine is large	If the work area on the machine is small	If the work area on the machine is restricted
Turning	FRUN* FRU	FRUN FRUB* FRU CS* FRC	FRUB CS FRC*
Turning and Milling	FRUN FRU	FRUN FRUB CS* FRC	FRUB CS FRC*
Cam and Crankshaft	KRHS*	KRHS
Heavy Duty	CS HL	CS HL
Grinding	AS* ASB*	AS ASB*	ASB
* First choice                # Steady model may vary for special applications