In the Pharmacopeial Forum, PF 52(5), the USP has published its responses to comments on the Stimuli article “Characterization of Apex Vessel Geometries and Irregularities”. The original article examined the geometrical characteristics and irregularities of commercially available apex vessels used with USP Apparatus 2 in dissolution testing. The responses indicate that further studies are planned before scientifically justified specifications and tolerances for apex vessels can be established.