This solid state thryratron is a replacement for C3J/5632 and C3JA/5684 vacuum tubes. The physical form factor is the same as the original glass tubes. The replacement will plug into the same socket as the original tube, and uses the same anode cap.
Original glass C3J vacuum tubes are still fairly inexpensive and easy to find as new old stock, however, the Scissio solid state replacement offers several advantages including 22 watts less quiescent power consumption, lower forward voltage and on state power dissipation, no warm up time, and more consistent switching threshold.
In the case of the modular drive version of the Monarch 10ee lathe, installing a pair of Scissio C16J tube replacements along with a C3J tube replacement effectively converts the lathe control to a completely solid state drive. Without vacuum tubes and their associated filaments, the control generates less heat under the headstock. With a full complement of tube replacements, the machine also no longer requires a one minute warm period for the vacuum tubes. You can take advantage of this by bypassing the TMR1 warmup timer with a simple jumper. This allows you to power on the machine and then immediately turn on the control without any warmup delay.