Considering some of the negative reviews, I am going to give a rebuttal since I once thought negatively of them also. I just came into some information that restored my faith in them. To all those purchasing these pilot erasable items (including their erasable pens), their ability to be erased lies with the fact that they utilize Thermo-sensitive ink that is removed by erasing friction. So, for some, like me, who left my highlighters in my hot car on a sunny day in Houston,TX, they may seemed to have stopped working. However, a note from their website reads: "Do not expose to extreme temperatures (<14 deg F; >140 deg F). If pen is exposed to temp that reaches 140 F, the ink will be colorless when writing. To restore color, cool to at least 14 F in freezer and the ink will again write in color."
So, I put my highlighters in the freezer (even though the note initially said do not expose the highlighter to <14deg but later says to put it in the freezer <14 F to restore color). Voila! Color is back and they highlight and erase as before.
Although, I'm not sure if this is actually the case with the negative reviews, I suggest those reviewers try the above before giving this really cool revolutionary product the shaft. If you did this and you're still having problems, then so be it, but at least point that out.
I gave this product 4 rather than 5 stars because I tried to contact the company a week ago when this happened by phone and by e-mail but still haven't received a response. Further, the package didn't mention the temperature sensitivity. Had I known, I wouldn't have been without my highlighters for the last week.