How cool is this?! Such a great tool for parents and practical for anyone working with kids on handwriting with letters or numbers. They also have speciality ones for math and music are also really cool options! This size is the 3/4 inch dashed roller. It's the only one I've personally tried, but the other options are worth checking out! I reached out to Legiliner and they said this about how long the ink lasts: 'Depends on the size of the barrel (which LegiLiner you have) and how much you use it. Small ones are 3-6ish months. Medium ones are about a school year' LTKhome LTKfamily LTKkids