NMR is a magnetic field sensing technique, and consequently, the design of an NMR probe must by definition take into account the perturbing effect that the detection elements will have on the (otherwise homogeneous) magnetic field (B₀).  In conventional tube probes, the container that holds the sample is removed and re-inserted with the sample each time a new sample is introduced.  Mechanical tolerances (air gaps) are required to facilitate tube loading, and the introduction of a new container with each new sample means that tube-to-tube disparities must be compensated as part of the shimming process.  Protasis probes utilize flow technology to introduce the sample.  This enables the use of a consistent sample containment geometry (the NMR flowcell) that does not change from sample-to-sample.  In turn, this enables a design approach where the mechanical structure of the flowcell can be optimized for magnetic match with less variability experiment-to-experiment, resulting in higher resolution and greater S/N than would be possible at this size scale if a more mechanically-complicated, tube replacement geometry were employed for sample loading.  CapNMR probes generally do not require re-shimming from sample-to-sample, provided that a consistent solvent is employed.