My London Fog has a zip in liner. It's nice because it allows the coat to work for slightly cooler days. The sleeves are too short and I am not in love with the color. The liner is fairly thin, making it good down to about 45-50F and it is tricky to zip into and take out of the trench. Cloth from the seam around the zipper easily gets snagged into the zipper prongs. It has served me well nonetheless, and I am looking for a replacement. I also have a TNF rain trench with a zip out liner. If I could duplicate it in a longer version I would. I can wear it down to about 32 degrees so it's good for cold rainy days. Without the liner, it's made of a Gortex like material so its waterproof. My TNF is mid length, and can fit over my mid knee length dresses but I need something longer for my Midi's. The liner zips in and out easily, and the entire trench is machine washable. I have washed mine multiple times and it comes out looking as good as new.
