Plastic Brain Jello Mold Fun World brain jello mold halloween party decoration. Make your own gelatin brains. Shock and terrify both your halloween friends and your normal friends with jello brains. This jello mold will freak kids out, too. Use delicious gelatin and make tasty brain treats. Realistic looking, this mold measures 9.75" x 8.5" x 4". For even more icky fun, use with our heart and hand gelatin molds.