The Sip-Tip valve helps straws stay full of fluid, reducing the amount of air ingested and effort required. The one-way valve can be trimmed at designated areas, giving the user selective flow restriction. Valve and lid are compatible with most brands of disposable flex straws. 8oz.spill-resistant tumbler has a graduated scale to monitor intake. Not recommended for corbonated beverages. Optional mouthpiece ensures proper placement, assists with lip closure and can be shortened to aid oral motor development. Microwave and dishwasher safe to 180 degree F.Latex free.