Great cup! The 360 spill-proof rim is truly amazing. It works the exact same way as the plastic version, but the base is stainless steel, which is awesome from a safety perspective. (The sieve piece is still plastic, but the liquid does not come into contact with that piece unless your child is actively drinking, so that's good enough for me) I'm attaching a few pics so you can see how it works, as well as one of my kid drinking while lying down. If she does this, she may get a few drops on her sleep sack, but no big spills. Unfortunately, so far Munchkin has only released a stainless version of the bigger 10oz. cup (with no handles -- see photos of stainless tumbler with green plastic collar and green top in my photos), however the lid is interchangeable with the smaller 7oz plastic cups (see photo of blue plastic cup with white collar/handles and blue top), so I simply use the stainless steel base with the handle top (see pic of stainless steel tumbler plus white plastic color/handles and blue top). I also love that this new model comes with a lid (that snaps on over the colored mouthpiece). The plastic versions, for some reason, do not, and it really makes all the difference in terms of preventing accidental spills in your diaper bag (without the lid, there's potential for something to push up against the rim and release some water). What else can I say, besides this is currently my kid's (22mo) favorite cup. She seems to prefer it at the moment to her straw cups. I'm also attaching a pic comparing size vs. a number of other popular sippy cups: BACK ROW, L to R: Camelbak Eddy, Thinkbaby Thinkster (stainless), Skip Hop, Munchkin 360 stainless (with handle top). FRONT ROW, L to R: Munchkin weighted straw cup, Oxo Tot, Pura 4oz straw cup, Thermos Foogo. FWIW, here are the other "non-toxic" sippy/straw cups we've tried, and how they compare to the Munchkin (aside from the obvious difference that they are all straw cups, whereas the Munchkin is a trainer cup that must be tilted to drink): - Thinkbaby Thinkster stainless straw cup (thinkbaby Thinkster Steel Bottle, Silver ): Good size (10oz), it works well and is leakproof as long as you make sure the valve inside is properly covered. Handles are a little overkill maybe and don't fit into deeper cupholders. - Pura straw cup(Pura Kiki 11 Oz / 325 Ml Stainless Steel Bottle With Silicone Straw & Sleeve, Pink Swirl (plastic Free, Nontoxic Certified, Bpa Free) ): I like it and it's truly leakproof, but it doesn't have handles so harder IMO for a baby/toddler to grip. Only sippy cup on the market with zero plastic parts (the internal straw is silicone), which is cool. I also like that you can swap out different mouthpieces (bottle nipple, sippy spout, etc.) to grow with your baby. It's shown in the picture with the smaller (4oz) size, but there are also larger (10-12oz) sizes available (in both regular stainless steel and double-wall insulated) - Thermos Foogo (THERMOS FOOGO Vacuum Insulated Stainless Steel 10-Ounce Straw Bottle, Blue/Yellow ): Great cup. Our favorite for preschool lunch. Truly leakproof, and cap is attached so there are no pieces to lose. Also very easy to wash as there are only 4 parts (tumbler, lid, mouthpiece, straw). Note internal straw is plastic (I bought a silicone straw to swap in to avoid potential leaching issues). No handles, so maybe harder to grip for a baby/toddler. - Green Sprouts Sip n Straw Cup (Green Sprouts Glass Sip & Straw Cup,4 Ounce ):Glass inner tumbler encased in plastic. It's OK, but has way too many pieces on account of the additional plastic protective layer. Also not easy to travel with. Many parents have also reported breakage (though I haven't had that problem). On the plus side it comes with both a sippy spout and a straw top to grow with your baby...however the size is pretty small (4oz), possibly too small for some toddlers. - Caveman Cups (Premium Stainless Steel Kid Cups Toddler Baby Sanitary Rimless Design 8oz 4Pack ): I LOVE these open cups for my preschooler, but I don't give them to my toddler often for obvious reasons (no spill protection). Totally recommend if you're in the market for an open cup, though. Great, compact size, and have a fluted rather than rolled rim so no gross stuff can collect there. The sides don't flex, which seems to minimize accidental drops here. I even find myself reaching for them for me to use for myself, when I need a smaller juice glass size. - Kinderville cups (Kinderville Little Bites Cups (Set of 2, Blue / Orange) ): Silicone open cups. Nice small (juice/kid cup) size. Overall I like them, however two minor issues cause me to reach for the Caveman Cups most of the time instead: 1) the walls are on the thicker side, which I think makes them slightly less comfortable to drink from, and 2) the silicone material flexes, which has caused my 4yo to drop them a few times by accident (i.e. when it gave in a way he wasn't expecting). I'd still reach for these over a plastic tumbler due to the safer material, however.
