I always find this confusing, don't think I've ordered the same thing twice.
Do we go with a low ohm part that will Hold at 500mA and trip at something higher? Or hold lower, like 250mA, and trip closer to 500mA?
Hold 350mA, trip at 700mA http://www.digikey.com/product-detail/en/0ZCC0035FF2C/507-1497-1-ND/2165326
Hold 250mA, trip at 500mA http://www.digikey.com/product-detail/en/0ZCC0035FF2C/507-1497-1-ND/2165326