THICKER BOROSILICATE MATERIAL | HEALTH SAFE| NON -TOXIC | BPA FREE - It is made of food-grade temperature-safe borosilicate Glass. Borosilicate Glass is meant to be light-weight but we have tried to make this DIAMOND PITCHER the Thickest it can be made. It has been strengthened using a special process called Annealing whereby the glass is heated to high-temperatures and then allowed to cool downed slowly.