The "slimline" series are slimer than the other series, and feature a straight clip with a center ring. The "slimline" pens/penciles are have very many ways to customize, such as custom bands or clips (For full details and pictures on custom bands and clips available, click here), and there are several different types plating (For full details and pictures on different types of plating, click here).
"Slimeline" pens/pencils: $20
Custom "slimeline" pens/pencils: $25
Note: "Slimline" pens use Cross(r)-style refills, and pencils use .5mm trouble-free lead, both of which can be viewed by clicking here.