Results of a critical state line testing round robin programme. Issue 12 (1st September 2021) - Reid, David; Fourie, Andy; Ayala, Juan Luis; Dickinson, Simon; Ochoa-Cornejo, Felipe; Fanni, Riccardo; Garfias, Juan; Viana da Fonseca, António; Ghafghazi, Mason; Ovalle, Carlos; Riemer, Michael; Rismanchian, Amin; et al.