The Siemens 3RH2122-1AT60 is a SIRIUS auxiliary contactor — size S00 frame, with 2 normally-open instantaneous contacts rated 10 A at 24 V. It's the switching block that mirrors or extends the main contactor's state in a control circuit, not a power-handling device itself. The S00 footprint (45 mm wide, 73 mm deep, 57.5 mm tall) keeps the cabinet fill factor tight — you can stack several across a row without crowding the gland plate.
The 30 million mechanical cycles is the contactor's rated life without a load; under rated switching the electrical life will be lower but still well into millions, so it's not the wear item in a panel that sees a few cycles per minute. Surge voltage resistance at 6 kV means it withstands the transients common in industrial control panels without flashover.
That side clearance is the tight one — adjacent devices need that 6 mm gap for heat dissipation and tool access. Wire range: 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), or 2x 4 mm² solid/stranded; AWG equivalents 2x (20...16), 2x (18...14), 2x 12.