These refillable technical Pens are great for freehand sketching, commercial illustration, Note taking, precision drawing, etc. Rapidoliners tubular and radiused nib makes it suitable for all types of applications. Hold the Pen comfortably at an angle or straight up and down - either way, it moves easily in any direction on the drawing surface. The Pens are compatible with all Templates that have Inking lifts and suitable for all compasses with Universal attachments or those fitted with an adaptor. You can remove Rapidoliner pigmented Ink from tracing paper with imbibed block or strip erasers. The black Ink refill cartridges are disposable.