Recommended for: 18months+. With the Weighted Flex-Straw Cup, your kids can enjoy drinking from the bottles while sitting upright or at any position. It allows the liquid to flow with the straw, ideally teaches your kids to transition from bottle to cup. The 2-way valve feature prevents liquid to spill when turn upside down, making it safe, no mess or fuss. This also encourage and build their self confidence for independent use.