Mainstays 5-Pack Round Meal Prep Containers with Lids, 1L, BPA-Free, Microwave & Dishwasher Safe, Ideal Use for Meal Prep and Batch Cooking

I buy the single compartment rectangular ones of these all the time. I love that I can heat up my leftovers without having to take them out of the fridge container. I also like these round ones for making up quick bits like some instant mashed potatoes. In my mind, I have to have round ones whenever I'm doing something where I'm mixing dry into a liquid. Not necessary, just an OCD of mine. My DIL uses them to take lunch to microwave at work and she puts both parts in the dishwasher with no issues; my use is a bit different. I hate to wash dishes, so I make up a batch of one thing or another, fill a few of these, leave one in the fridge and the rest in the freezer until needed. Once I've emptied the container (these hold several servings for me), I throw it away (I use all paper plates and bowls, disposable plastic spoons and forks). The lids fit tight and stay on, even to the point where sometimes you have to work at it to remove the lid, but that's so much better than having an ill-fitting lid that won't stay on. They are surprisingly durable, so those of you who are not so wasteful as I will find them a better addition to your kitchen than the frosty ones with the red or blue tops, sold by trash bag makers.