Borosilicate glass

Borosilicate glass is a type of glass made with boron trioxide, which gives it a lower rate of thermal expansion than ordinary soda-lime glass. In practice that means it can handle a hot container going straight from the freezer into an oven, or a jump from the microwave to a cold countertop, without cracking as easily as a cheaper glass dish might.

In meal prep containers, borosilicate glass is the material behind claims like 'oven, microwave, freezer, and dishwasher safe,' since it survives the repeated temperature swings a container goes through during a normal week. When comparing glass options, check whether the lid is also rated for the same temperature range, because many lids are BPA-free plastic or silicone with a much lower heat limit than the glass base.

A common mistake is assuming all glass meal prep containers are borosilicate. Cheaper sets sometimes use standard glass that looks similar but is more prone to shattering with sudden temperature changes, so it is worth checking the product description rather than assuming from price or appearance alone. Even with borosilicate glass, avoid extreme jumps like taking a container straight from the freezer into a very hot oven.