The present disclosure relates to a filled silicone rubber material 2 including at least 20 wt % of alumina tri-hydrate as a filler 4 dispersed in SiR 5 to below the percolation threshold. The ATH is a mixture of a first ATH powder and a second ATH powder. The particle size distribution of the first and second ATH powders are such that the d90 value of the second ATH powder is less than the d10 value of the first ATH powder. The disclosure also relates to an insulator 1 made from the filled SiR material 2, and to a use of the insulator in a high-voltage direct current application.