If your STAEDTLER Textsurfer Classic highlighters are running low on ink it is easy and clean to refill them using STAEDTLER's refill station. Simply uncap your highlighter and firmly press the end with the tip into the top opening of the refill station. Minutes later it is ready to use, or after 3 to 4 hours it is completely refilled. Overfilling is impossible as the highlighter can only draw its maximum ink content out of the refill station. Does not spill when tipped over during refilling. Since the Textsurfer Classic's body and cap materials guarantee a long service life, why not be easy on the environment and refill them when possible! STAEDTLER's INK-JET SAFE ink will does not smear ink-jet printouts and handwritten text. NOTE: This refill station is intended for use only with STAEDTLER Textsurfer Classic Highlighters wtih INK-JET SAFE ink. Bottle contains 30ml of blue ink.