The best storage jar is rectangular in shape because it doesn"t leave any dead space in the fridge. Second, the knob of the Bistro Storage Jar gradually adjusts to the airflow from completely airtight to breathable. And third, the middle of the lid is transparent so the jars can be stored in drawers without having to lift every single container up to check its side. They are made from plastic, silicone, and stainless steel and come in three different sizes.