In their article “Laser digitization of casts to determine the effect of tray selection and cast formation technique on accuracy” Drs. Brosky, Pesun, Lowder, DeLong, and Hodges (J Prosth Dent 2002;87:204-9) evaluate the accuracy of models taken with custom trays and stock trays and poured either upright or inverted. Evaluation of impressions taken with elastomeric impression materials indicate that there is no statistical difference with custom v. stock impression trays, or with upright v. inverted impression pouring.