This is a replacement weighted straw for the 160ml or 260ml Sippy cup. 

Care: To wash, you can remove the weight and sterilise the straw. To attach the weight again, you need to feed it on carefully, this takes a bit of time and patience but make sure the straw is pushed right up to the weight. Pull it to check it is secure, if it falls off then you will need to feed it up more.