While these aren't leak PROOF, they certainly don't seem to leak from section to section. I wouldn't cart soup in them, but they work just fine with yogurt, sauces, etc. The different colored lids are great for packing lunch the night before. My husband and I eat different amounts of food and with these he doesn't accidentally take my dainty lunch and I don't wind up with his lumber jack meal. They're perfect for separating things like your potatoes from your chicken or what have you. Also fantastic for sandwiches. I put my condiments in one section, veg in the other and that way it's not soggy by lunchtime. These are also a lot sturdier than the kind you can buy at the store like Ziploc brand. We've washed these a ton of times and the lids still fit and haven't warped, even after microwaving and the dishwasher.
Update- we liked these so much that we got another set! They' are AWESOME for separating a plate of leftovers so you don't have the second day soggy.