The Siemens 3RT6916-1BE00 is a SIRIUS surge suppressor with a varistor, designed to clip onto S00-size contactors and relay bases. It handles 240-400V AC at 50 Hz and 400-240V AC at 60 Hz — the voltage range flips with frequency because the varistor's clamping threshold is frequency-dependent. This is the part you add when the coil is AC-powered and you need to suppress switching transients at the source, not downstream.
At 9 mm deep, 28 mm wide, and 46 mm tall, this suppressor occupies barely any DIN rail space — it clips onto the contactor's front, not the rail itself. The S00 frame size is the key constraint: it fits only S00 contactors and relay bases (Siemens 3RT1 and 3RH1 series in that frame). It will not physically mount on S0, S2, or S3 frames. The varistor design means it clamps voltage spikes from the coil's magnetic field collapse; for DC coils you need a different suppressor (typically a diode or RC snubber).
Clip-on mounting to the contactor — no DIN rail footprint consumed. Mount in any position. The suppressor adds negligible height to the contactor assembly; verify clearance above the contactor if the panel has a shallow lid.