A stylus normally consists of three components:  Adapter, shaft and stylus tip

The adapter

The adapter is the connection between the connection thread and the shaft. It is important that the adapter is designed in such a way that it can withstand the measuring force that is introduced via the shaft in an optimum manner. Otherwise there will be an increased scatter of the probe measurements. In addition, the connection point to the extensions is always undercut to ensure optimum force fit. 

Depending on the measuring system being used, ZEISS uses M2, M3 and M5 connection threads. 

Conventional M3 styli may not be used in XXT stylus systems; the M3 XXT styli which are optimized for passive scanning should be used instead. The 1 mm larger diameter of the XXT adapter base body and the high-strength titanium alloy guarantee a considerably higher stiff ness compared with conventional M3 styli.

The shaft

A distinction is made between a straight and a stepped shaft in the design. The stepped shaft has the advantage of as lightly greater shaft thickness DS, which reduces towards the stylus tip. The disadvantage is the smaller usable measuring range MLE with the shaft thickness DSE (compared to DS and ML with a straight stylus). The material and the cross-section have the greatest influence on the stylus stiffness, whereby the solid material is always stiffer than a tube. The key
characteristics in the shaft are stiffness, weight and thermal
linear expansion. The table shows that ZEISS ThermoFit styli
optimize these three characteristics.

The stylus tip

The stylus tip can be a sphere, a disc, a cylinder or a variation of these, such as a half-sphere or a cylinder with a ball end. 

The stylus sphere is the most often used stylus tip.