Two ROMs are supplied with the kit, a replacement ADFS ROM and a ROM Filing System chip of the hard disc format utiltity.
ADFS was written to expect SCSI-type devices on the 1MHz bus, but the Compact Flash drive uses an IDE interface, so a new version of ADFS is needed to run the drive. For the BBC Model B, this is ADFS 1.33, and upgrade from ADFS 1.30, and for the Master Series the standard ADFS 1.50 is replaced with ADFS 1.53. For the B you need to take out your existing ADFS chip and replace it with this one; for the Master, you can't take out ADFS as it's part of the system ROM, so it must be unplugged and the new chip fitted, or loaded into sideways RAM.
This is a 32K ROM containing both versions of ADFS so the same chip can be used on either machine.