IK Multimedia ARC Studio hardware in very good condition. No measurement mic included (£69 on Amazon). You will be able to register this product with IK Multimedia (there may be a small charge to transfer ownership) and that will enable you download the Arc X software for free.

ARC Studio is a standalone hardware processor for room and subwoofer correction. Connect it between your audio interface and monitors, run the ARC X measurement and calibration process, and hear your mixes with greater accuracy, independent of your DAW, operating system, or playback source. AKM Velvet Sound AD/DA conversion, 32-bit float internal processing, and 120 dB dynamic range preserve the integrity of your signal while ARC X correction addresses what the room is doing to it. Compact and self-contained, ARC Studio brings a trusted monitoring reference to any studio.