Use this chart to identify the model of your Classic Pen in case you want to order custom feeds and adapters that will fit your Classic Pen snugly.

If you are unsure of the identification of your pen, send a picture of the pen to identify_pen@ackermanpens.com. Make sure to include the flange around the pen in your photo. The flange displays cross-hatching marks, also called "knurling". We use these marks to identify each model.