I put mine in a sealed ziploc bag with air removed, then put that in a mason jar that has a handle and fill it with hot water, then put that cup in a big bowl of hot water, that way it stays sunk below hot water instead of floating in the cup. That way if the water in the cup cools off the hot water in the bowl keeps warming it. It takes about 5-10 minutes for small mice and about 20 for a small rat and our snakes haven't refused food yet.