These ice cube trays are made of hard plastic which makes round ice cube easier to release than silicone ice cube mold. After taking the mold out of the freezer, open the lid and slightly twist the tray to release the ice. The circle ice cube mold consists of one tray and a lid with small holes. Just pour about 380ml of liquid into the tray at one time and close the lip. Then put the mold into the freezer for 4 hours. Our ice cube molds are made of high-quality food-grade material. BPA free, no smell, no toxic. Safe and durable.