When installing a solar array, you intend the installation to last many years. When mounting items such as string array cables it is now prohibited to use plastic cable ties according to AS/NZS 5033 (Plastic is just not designed to last long term outdoors in a flexing application). Therefore stainless steel cable ties are the better option. Some basic cable ties are bare metal and are quite sharp, however these cable ties have a black Epoxy coating so they have rounded edges and are less likely to cut into cables.