The 5SV8900-1KK solves a simple mechanical problem: the 5SV8 residual current monitor transducer does not have a built‑in DIN‑rail clip, and you don´t want to fix a measurement device with cable ties or double‑sided tape. This holder snaps onto any 35 mm rail and provides a firm seat for one 5SV8 transducer. Click the holder onto the rail, slide the transducer into the holder — the electrical connections remain untouched, and the device sits flat against the backplane. At 5 g it is light enough to be shipped as a letter, yet rigid enough to hold the transducer in place through vibration and thermal cycling. The holder is supplied individually; ordering two gives you a set for a main and a backup RCM in one go.