HP Plotter Pen Rapidoplot E 6820 Series for Hewlett Packard Plotters FOR HP 7550A. HP 7550B. HP 7570 HP Draftpro. 7580A. 7585A. 7586A, 7595A, 7595B, 7596A, 7596B. 7599A, HP Draftmaster 1.11. MX. RX. 5X. HP Draftpro DXL (7575A). HP Draftpro EXI (7576A). Roland DXY Series. and other similar plotters. The Hewlett Packard Rapidoplot 6820 Series E Style Plotter Pens is a 2-part system comprised of the nib and a pre-filled ink cartridge. Inks are permanent, pigmented systems that conform to standards for achievability.