From https://www.microsoft.com/accessories/en-us/products/mice/microsoft-classic-intellimouse https://www.microsoft.com/accessories/en-us/products/mice/mi... 5

From https://www.microsoft.com/accessories/en-us/products/mice/microsoft-classic-intellimouse https://www.microsoft.com/accessories/en-us/products/mice/mi... 5 buttons (3 customizable * ) * Customization not available on devices running Windows 10 S. Hadn't heard of Windows 10 S before this. Looks like an attempt to convince people to give MS iOS-like control over their PC in the name of security.