PTFE-coated tips are primarily used for fluids with a higher surface tension that tend to wick up the outer diameter of the cannula of a standard general-purpose tip. When you’re trying to make a small deposit, and part of it wicks up the cannula’s OD, the result will be an inconsistent deposit. After a few dispense cycles, the fluid buildup that has collected on the cannula’s OD will fall off, creating a larger deposit on your part. The PTFE coating lowers the surface tension of the cannula and prevents the fluid from wicking up the tip, resulting in very consistent dispenses.