NIRS Probes and Caps must be fit properly and comfortably Caps must be snug but comfortable. An uncomfortable subject will not hold still, or give good data. Many NIRS probes are incredibly uncomfortable and can only be worn for 30 minutes at the most before subjects must take them off. Not only are our standard probes comfortable, but we also offer specialized probes for long-term measurements and NIRS measurements on infants and children.