The SENTRON 5TT5902 is a sealable end cover for the Insta contactor family — specifically the 5TT5 7 series DC technology contactors rated at 24 A. One set ships as two covers, enough to cap both ends of a contactor or a small group in a DIN-rail enclosure. This is the cover that goes on the terminal side of the contactor after wiring, letting you seal the connection area. Useful where a panel needs tamper-evident or dust protection on the line-side terminations, or where an inspector wants to see a seal after commissioning.
No second-source cross-reference needed — it's the OEM part for that family.