above primarily refer to diameters, in other examples, the catheters described herein may have cross-sectional shapes (the cross-section being taken in a direction orthogonal to a longitudinal axis of the respective catheter) other than circular. In these examples, the inner and outer catheters of an aspiration catheter system may have the same relative configuration (e.g., the inner catheter being configured to be received in an inner lumen of the outer catheter) and same functions described above with respect to catheters having circular cross-sections. 

