I bought my trackball because I didn't have enough space on my desktop to use a mouse and I had used a track ball before , but a different model. I'd used the track ball for about six months and I noticed my forth and little finger were getting numb , I thought what am I doing differently so I tried to change the way I was holding the track ball but the numbness still continued , so I stopped using the track ball all together and the numbness finally went away .I'm right handed so I guess this track ball just wasn't meant to be for me.