Ritchie omnifount. A plastic fountain with stainless steel trough. The last one I bought was about $550, although that's been several years. Clean it periodically, but otherwise a low maintenance waterer, even at -20 degrees. I've also got the all plastic Ritchie fountains with drop in heaters, but they can freeze up when the wind is blowing hard and I've had problems with water seeping around the drain plugs.