The SP80 and SP80H do not use absolute encoders. Therefore, when you power off the probe the encoder's position is not remembered. This means that when the probe is powered back on it is necessary to re-home the probe.
The SH80K is a device with a kinematic location ball that allows you to power off the SP80 and SP80H probes and turn it back on without needing to re-home the probe. This is achieved by fitting the SH80K before the power is switched off. The kinematic location ball locates into a kinematic location screw that is fitted to the probe and therefore holds the probe mechanism in a fixed position. This means that the readheads remain in a fixed position and therefore the probe does not need to be re-homed on power up.
The SH80K can be fitted to the probe either manually or automatically using an SCP80 / SCP80V.
It is possible to use SH80K with any SP80 or SP80H probe, providing you fit the kinematic location screw to the probe body.