It's a long resistive wire that gets attached to the eaves of your roof to melt any ice that gets up there. If you have a choice, get the lowest power rating wire you can find. You don't want to melt the raingauge. Take 8 popsicle sticks and attach them vertically to the side of the raingauge at 45 degree intervals. This will keep the wire from touching the raingauge plastic.
Some wires can get hot enough to melt the plastic.
Also make sure that the coils don't contact the plastic. Avoid touching the feet with the wire. If you have enough wire, you may want to loop it over the lip of the gauge and down into the screen area. Don't touch the plastic edges of the gauge with the wire. When securing the wire, use high temperature silicone glue.