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 Steven Latham

EDIT:I have since found the original blue ball and I have to say the original is by far the better one. The one that I bought as a replacement tracks sooo slowly I had to raise my cursor speed from 10 to 16 just to get it to work relatively normally, but it is kind of stuttery and if anyone tells me to clean the nubs inside or clean the little laser inside, I already have. It's still slow and stuttery. I'll be sticking with the original ball, regardless of how nice the new one I feel I wasted $10 on is.ORIGINAL:I have an M570, I've had it for a few years now, love this mouse.Recently lost the trackball due to my cat knocking the mouse down and the ball popping out and going who-knows-where, bought this as a replacement after reading people saying it was a bit too small or it didn't roll smoothly or something else, but I personally haven't had any problems with it, it fits perfectly in the hole, and it looks better than the original blue ball!I haven't had any issues, thankfully, and for the price, I'd buy more of these with no purpose other than to change them out with my moods, lol. Oh! Also, it comes in a really small box with foam that's fit to hold the ball in place, so if I ever find that other ball I'll have a nice little box to put it in, might paint it to make it look nicer or something, but it's great! Super happy to have found these!