Glad Food Storage Containers - Family Sized Container - 104 Ounces - 3 Containers : Amazon.ca: Home
Here's the purpose of the circle on the Glad salad container lid
Glad Soup & Salad Food Storage Containers, Medium Rectangle (24 Oz) - (Pack of 6, 30 Count) | Strong and Durable Food Containers from Glad for Everyday Use | 24 Oz Food Storage Containers : Amazon.ca: Home