What it is
It is a legacy platform unit — the listing names ASEA BROWN BOVERI as the OEM and carries the part code ACS800-U1-0020-5 across both title and description.
The only number that lands in the cabinet
Mass is the single usable physical figure: 6.35 kgs for the ACS800-U1-0020-5, which is the load a panel-builder plans for when sizing the gland plate, the backplate fixings, and the lift path during a swap.
Where the platform sits today
Buyers commonly cross-shop the ABB ACS880-01-07A6-5 as the platform successor, and that part is also listed at 6.35 kgs — so the cabinet cut-out, fixing pattern and mass budget line up on paper. Whether the older ACS800-U1-0020-5 drops into a panel that was specified around the ACS880-01-07A6-5 without rewiring is not something the listing confirms; the 6.35 kgs match covers the physical swap, not the control terminal map, firmware or fieldbus option slot.
Frame context for the second-source question
The wider ACS880-01 frame siblings run from 4.54 kgs on the ACS880-01-11A0-5 up through 6.35 kgs on the -07A6-5 and 7.71 kgs on the -021A-5, which is the band a sourcing engineer has to bracket when the ACS800-U1-0020-5 is on the BOM and the panel needs a same-frame second source.