This sippy cup is my of my favorite for mature infants and toddlers. Optimal ages for First Years Tumble Mates sippy cup is ~14 Months to 4 years old or whenever the child is ready to transfer from a sippy to a traditional open cup.

The First Years Tumble Mates cups are 10 ounces in size which typically works well for kids in this age range. I have found that the smaller cups hold too little beverage requiring two separate cups be used for school and travel.

What I like best about this sippy cup is the fact that both my enjoy drinking from them so it helps them drink more milk and water. But the fact that my kids drink well from this sippy is nicely complemented by the cups ease of use. First Years Tumble Mates use a favorable two piece design. Most sippy cups have three parts:

1. Cup
2. Lid
3. No spill insert

The First Years Tumble Mate has a simpler two piece design of just a cup and lid. The lids had a very simple built in no-spill mechanism which is extremely effective. As such, with these sippy cups I never find myself scrambling around the kitchen looking for a small clear plastic insert to prevent the beverage from spilling out. Instead I just snap-on a good sized and colorful plastic lid that is easily located. This same design makes these lids easier to clean that others. There are now small parts to wash or tiny little areas to try and get clean.

Other important attributes of this sippy cup is that they don't break and the lids will not accidentally fall off. The plastic used in this sippy is flexible enough that there will not be any surprises.

One potential area for improvement is that kids that tend to chew on the drinking spout may wear out that spout in a year's time. When the spout wear out, beverage may come out when the sippy is held upside down and shaken. But this longevity factor in my mind is offset by the low cost of the product and the fact that the product works extremely to begin with.

The reason why I think this is the best cup for 14 months to 4 years is that it has no handles. So kids need to learn to use two hands. The advantage here is that kids learn how to hold a cup without handles and when they are ready this sippy easily converts a big kid cup, one the child is already used to.

Again this is my favorite sippy cup for infants and toddlers. Kids tend to like drinking from it, this sippy does not spill and its easy to operate. Can't ask for anything more than that in a sippy cup.

The lid on these cups leaks SO QUICKLY! The valve in the spot and the air release valve leak after just a month or two of use. We have four cups and ALL of the lids have failed. The cup is fine but no better than any other insulated product. The fact that there is no 3rd piece is nice--fewer little items to loose but the fact that the valves in the lid leak and I have little spots of milk/juice everywhere makes them terrible. I'm on line right now trying to find replacement lids in the hope that the two separate sets I bought had "bad" or defective valves.