100% Flexible silicone material, non-toxic, BPA-free, dishwasher-safe Stretch lids are made of durable silicone which provide strongly strethable to fit odd shape and size container, perfect For Rectangle, Round, Square Bowls, Dishes, Plates, Cans, Jars, Glassware & Mug Place half of the lids over one edge of the container.Start on the side closet to your body. Stretch the other half of the lid away from you,inching your way around the bowl. Stretch,then press the top of the lid while pulling the tabs to create a vacuum seal. Pull the sides to ensure a perfect fit.