I own the Signature CD mat and window dots, and have used a few of the tuning dots. All of them work, but to varying degrees. The tuning dots, which were used inside my CD player, changed the tonal quality to a degree I didn't like, though they did make the player slightly more transparent. Others have reported drastically good results. The window dots, which I still have on a doorwall, helped slightly, increasing image focus primarily. The CD mat has produced audible results on several players, but its efficacy seems dependant on the quality of the transport. For example, it has no benefit whatsoever when used in conjunction with TEAC's VRDS-NEO mechanism. In fact, it made things worse. But it definitely CAN help. Overall, I like Marigo's tweak products. They can help, but not always across the board. Just one man's opinion.