Question: What do you think of the two probes shown in Fig 1?

Answer: Observations about these two probes include:

• Probe 1 is well positioned on the finger. It fits well and is not too tight. the probe does not constrict the circulation. It is not too loose and will not fall off or let other light in.
• Probe 2 is too small for the toe, Forcing the probe on to a large digit in this way will damage it. The probe will not pick up the light.