Before Use: You are recommended to wash it before use, or some suggest to put it into oven for 3-5 minute if there is strong silicone smell. Step.1 Close the tray and try to lock the groove on the side of each skull Step.2 Fill in the skull with water from the top hole, sure you can make fruit jello or chocolate skull too Step.3 Put into fridge for about 6 hours !!! Extra Tips for Clear Ice Skull !!! As mentioned, pure water is one of the factor. Another key factor is you need to control how it cools. Try to chilling the water more slowly, you will more higher chance having clear ice skull. You can put it in refrigerator at lower temperature for hours and put to freezer for another 4-6 hours Practice make perfect Temperatures range: -40°F~450°F/-40°C~230°C Size : 4.44" x 3.15" x 1.57" (11.3cm x 8cm x 4cm) Skull Size : 1.57" x 1.77" (4cm x 4.5cm) Package: 2 piece Skull Silicone Mold