The Ultra Fine tip is amazing for highlighlighting and designing very fine details, whether lettering with simple or bold fonts, adding facial features,eyelashes, hashmarks, or small doodles on your cookie.  The bright, rich pigments used in the colored  pens with bring your design alive!  
Because the pigment in the pen was designed to dry instantly, all tweets Pens are smudge and bleed proof and will resist any extract, vodka or Everclear (due to their high evaporation content) when mixing with gel food colors, Luster, Petal, Matte and Metalic dust powders. Painting with water is not recomended.  Pens are designed to be used on dry Royal Icing, Dry Fondant, Wafer Paper, FlexFrost Fabric, and Gumpaste.
All pigments are FDA compliant and labeled non-toxic and should be considered for decoration use only. Non-toxic means it isn't toxic if ingested and the ingredients are not absorbed by your body.