The Uniball 207 is a retractable, gel rollerball pen and was introduced by the Rubbermaid company as a fight against check washing. Check washing is a process used by thieves in they erase the ink on a check (usually with a solvent) then rewrite it to make fraudulent withdrawals. In 2006, check washing led to 800 million dollars of fraud in the US. The Uniball 207 protects against check washing because of one main reason: it uses a pigment-based ink, as opposed to a dye-based ink. This means the pen ink adheres to the surface it's writing on, whereas the other types of ink sit on top (thus making it easier to wash). If you already have a favorite rollerball pen, the 207's ink cartridge will fit in most encasings. The Uniball 207 comes in either a 0.7mm tip or 0.5mm tip.