Unfortunately, this trackball loses the ability to maintain the left click after about 2 to 3 years, which makes click-and-drag operations risky... the problem appears slightly at first and gradually worsens... in our company the problem is renewing over 6 copies bought at different dates and via different suppliers and several youtube videos show how to fix the problem: https://www.youtube.com/watch?v=0cihhU4g74c but it's not my cup of tea... shame apart from that it's an excellent product but I wouldn't buy any more at that price.