With the vinOwriter pens, you will never lose track of your wine glass again. At your next party, Get the bestselling Cork Pops, vinOwriter 2 pk and let your guests express themselves - and practice safe sipping. May be used on any non-porous surface which can be cleaned with soap and water. Does not rub off! Perfect to write a message on the bottle of wine you are gifting. You can also use on cheese plates to identify the cheese, leave a love note on the bathroom mirror - or even some driving instructions on the windshield of that car that just needs some remedial help!