What is the part number of a 30mm diameter pushbutton blanking plug (closing plate)?
For the Harmony 9 (9001K series) 30mm range, there are 2 blanking plugs (also known as 'closing plates') available;

The part number of a blanking plug from the legacy XB2M 30mm pushbutton control range is the ZB2SP02, these are still available. The ZB2SP02 is exclusively for use with XAPM** control stations that have 30mm cut outs. A seal and fixing nut are supplied with the blanking plug.
- 9001K51 - Grey finish
- 9001K52 - Chrome plated finish

The part number of a blanking plug from the legacy XB2M 30mm pushbutton control range is the ZB2SP02, these are still available. The ZB2SP02 is exclusively for use with XAPM** control stations that have 30mm cut outs. A seal and fixing nut are supplied with the blanking plug.