Re-Play's Straw cups have a screw on lip with circular opening for the bendy neck straw. Insert the straw from inside the lid before screwing on to the cup to ensure that it won't slip out as your child moves around.
Like the sippy-cup, the shape of the cup, thinner at the base tha at the top, makes it easy for small hands to hold and the surface is textured to prevent the product from slipping.
Each cup can hold approximately 300ml.