In 2017 more muon-sensitive emulsion plates were positioned in the descending corridor and in Al-Mamun's tunnel. The void behind the chevrons could be confirmed through different points of view and its characteristics refined. Named "ScanPyramids North-Face Corridor" (SP-NFC), this void is located between 17 and 23 metres (56 and 75 ft) from the Great Pyramid 's ground level, between 0.7 and 2 metres (2 ft 4 in and 6 ft 7 in) from the North Face. It could be horizontal or sloping upwards and it has a corridor-like shape.