hmm . . . what is missing from this picture?

What is missing from this gel-pen roll?  (For my second roll, I made a gel-pen roll instead of a crayon roll.  It was quite the adventure in absent-mindedness, but more on that later.)  

This is another guessing game, and I've got a poorly made crayon roll or gel-pen roll for the lucky winner.  Here are the rules for the game:

1) Post your guess about what is missing from this gel-pen roll below.  Make sure your name is somehow associated with your guess.  You might need to include that in the post because I think your name only shows up automatically if you sign in with your google account.

2) I will take all the correct guesses submitted by Tuesday at 11:59 PM Central Time and draw one name randomly as the winner of a poorly made crayon roll or gel-pen roll.  The roll will be fully compete and usable, but I can't guarantee it will be flawless.  I'll contact the winner for an address if it needs to be sent.  Wow!  What a deal!   

Craft on!