Leslie 122 and 21h speed control relay - this is the unit that mounts inside the amp chassis and replaces the mechanical solenoid. It mounts in the same hole.
This auction is for TWO of these units. I do not know if they work, when I rebuild a 122 amp, I only use the Trek II switching kit. It’s $100 but it’s bullet proof. These are much cheaper and can work well, but I prefer the Trek unit - it completely eliminates the 2nd 12aux7 tube.
Both of these units are used and I haven’t tested them. Please take that into consideration!!!