High Quality Hand Blown Borosilicate Glass Replacement Lid Borosilicate glass is well known for its durability and resistance to thermal shock This means it will not crack under extreme temperature changes like regular glass. It has the ability to go straight from a freezer to an oven rack without cracking. For you, this means you can pour boiling hot water into borosilicate glass Mug without worrying about shattering or cracking the glass. While Borosilicate is far more durable and resistant to thermal shock than other types of glass, it is glass so breakage is still a possibility. Borosilicate glass is hypoallergenic, lead-free and unlike a plastic straw, it is BPA-free. Have peace of mind knowing that no toxins are being leached into your beverages as you consume them! . High-quality FDA Food Grade Tested Silicone Silicone Seal to prevent any leaking while drinking Worry FREE Purchase as we stand behind our products with our Unconditional Satisfaction Guarantee Click "Add to Cart" now to drink your perfect cup of coffee