The replacement straw length is already suitable for the 10oz cup and does not have to be cut. Follow these instructions to cut your replacement straw for the Philips Avent Bendy Straw Cup 7oz.
1) Place your replacement straw on the side of the packaging (see image below)
2) Make sure the bottom of the replacement straw is aligned with the bottom of the straw on the side of the packaging
3) Cut the straw as indicated