Shape of vaginal suppositories affects willingness-to-try and preference

► 99 Sexually active women evaluated 5 microbicide prototypes in the laboratory. ► Willingness to use and ranked preference both differed as a function of shape. ► Even when volume was constant, perceived size varied as a function of length. ► Despite constant formulation perceived firmness varied as a function of width. ► Two promising candidates were identified for further optimization.