Pencil can be used with the iPad 2, 4 and Mini models; Microsoft OneNote is a software program that can be used with the Pencil using the iPad 2, 4 and Mini models; Drawing tool for iPad; works with the Paper by FiftyThree app and the Microsoft OneNote app installed on the Library iPad 2, 4 and Mini models; Adaptive palm rejection knows whether it's your hand or Pencil touching the screen; Write from any angle without requiring any calibration or set up; Unique built-in eraser lets you precisely carve away to get at what's essential; no need to switch tools, just flip Pencil to erase; Surface Pressure Expressive from every angle, so you can create lines of all sizes without any settings; Just touch Pencil to iPad screen and "Kiss-to-pair" connects; Sleeps automatically and reconnects whenever you open the app; Battery charge lasts about a month under normal use.