The STL 20M is our latest mono STL transmitter. This transmitter replaces the STL 10. There are a number of changes that were made to make this the price-value leader in mono STL products. The STL 20M is synthesized, has a new RF amplifier, as well as a cooling fan. More power, reliable, cooler, and easier to tune - that's the new STL 20M. Two of these units can be used to build a discrete stereo STL system.