Review on Perixx PERIPRO-303 X4A Trackball With 1.34-Inch Replacement Ball For Perimice And M570 - 4-In-1 Multi-Color Trackball In Red, Purple, Pink, And Lavender With Stylish Storage Box by Jeremiah Whiteley

This fits into the M570 or M575 just fine. And looks great! Works fine!I found the one I received to be a bit 'sticky' out of the box. I've wiped it several times with a couple of different soft microfiber cloths and it has helped but it still feels just a bit 'tacky' to my finger.This is in comparison with the balls in the M570 and an older Logitech "Cordless Trackman Wheel" that I have which both feel really smooth to the touch.Maybe it needs a little break-in period. I hesitate to 'clean' it with any kind of cleaning product (Windex or similar) because I don't know what that would do to the surface of the ball. Maybe I'll try just a moist paper towel and see what that does.