Munchkin Mighty Grip 10oz Sippy Cup tell your kids to get a grip when they sip. This fun-to-grip contoured cup makes it easy for little hands to hold and sip a favorite drink. Tipping won't spill this leak-proof cup with It is a built-in valve. The valve is made of soft silicone, so it's very comfortable for your growing child. This is one unique cup with a mighty big advantage.