Writing compatible with all capacitive touch screens: iPads, iPhones, MacBook Trackpads, Magic Trackpads, HTC, Samsung, Nokia, Motorola, Blackberry. Pen side is refillable with Jot Flip ink cartridges (sold separately). Sound dampening tip simulates the feel of writing with a pen on paper, while also making your strokes quieter. Small plastic disc at the tip of the Jot should not be removed; disc is replaceable. Replacement caps and discs can be purchased separately on Adonit’s site.