Press the soft rubber button to release a small amount of liquid. The soft rubber button release on the Feeding Cup allows control of liquid flow and intake. Cup holds 8 fl. oz. (237ml) and is marked at 4 fl. oz, 6 fl. oz. and 8 fl. oz. (118ml, 177ml and 237ml)levels. Hole in the spout measures 1/16" (1.6mm). Replacement buttons are available in a package of 12. Institutional dishwasher safe and autoclavable.