Quick side lead advance with a durable eraser. It is the smoothest and darkest writing compared to other BIC mechanical pencils. Assorted .5mm 2Pk Mixed Chip barrel colors include: Black/Green or Blue/Red. Assorted .5mm 4Pk barrel colors include: Black, Blue, Green, and Red. Assorted .7mm 2Pk Mixed Chip barrel colors include: Blue/Red, Green/Yellow, or Pink/Purple. Assorted .7mm 4Pk Mixed Chip colors include: Blue/Green/Red/Yellow or Blue/Pink/Purple/Red.