The Intuos4 Pen Accessory Kit from Wacom is a bundle of spare parts for use with the Intuos4 Grip Pen.
Thick-Bodied Rubber Grip for Use Without Side-Switch
Standard Rubber Grip for Use Without Side-Switch
Standard Black Nib
5 x Stroke Nibs
5 x Hard Felt Nibs
5 x Flex Nibs
2-Year Limited Warranty
This works with pens from:
Intuos5, Intuos4, Cintiq 21UX (second generation DTK2100 only), and Cintiq 24HD only. This will not work with pens from Intuos3, Intuos2, Intuos, or Cintiq 21UX (DTZ2100).
More information about Wacom Products (Link to Wacom Website)