The radio power-mass plane is shown for radio relics with the double relic host cluster redshifts shown in colour and symbol size scaled with the largest linear size of the relic. The SE-relic in A3399 is shown (labelled SE). The flux density of the NW relic could not be unambiguously measured and hence is not shown in the plot. The candidate relics in the RXC J0232.2-4420 (labelled S-R and E-R) are also shown. These being outliers is an indication that these are not associated with the cluster (see Section 5.4). The literature sample of radio relics is from Kale et al. (2017), Dwarakanath et al. (2018), and Parekh et al. (2020).