The tests were done without a mat, on a table, where another mouse, which cost a third less, also optical, worked perfectly. If you are an adequate person who reacts to reviews, it is better to refrain. Has some pros: Only silence LMB, RMB, design, colorless optics. Good sadistic weapon from Logitech. If you like to suffer from products of low quality and high prices - I recommend. If you want to suffer subtly, from square circles and broken straight lines, take it without hesitation either. If you want to show tricks, how a broken line is drawn under the ruler with the mouse - take it! Got cons: It costs too much and works too poorly to be called a mouse. I repeat, it is impossible to draw a straight line, even under a ruler!