Do not buy

$5, and no online support on how to actually connect the darn thing. Until this is added, its really not worth your time. If youre getting this to help with Sibelius on a MacBook Pro, go change the input settings by going to File (Sibelius tab on Mac) > Preferences > Keyboard Shortcuts, then choose the Notebook (laptop)
features feature set (tab in upper-center of window). This lets you use the numbers at the top of the native qwerty keypad, free of charge.

MatthewBillman about NumPad., v4.0.1