Yes Snugglesafes are a brilliant invention! I have 4 for my 5 piggies. I have outside piggies and in the winter I pop all 4 Snugglesafes in the hutch around 4-5pm and in the morning I reheat them around 7-8am. I know that they help my piggies through the worst of the cold along with snuggle sacks, fleecy tunnels, and snuggle beds, loads of hay, 2 thermal hutch covers and a blanket to keep out the frost! The only time I have ever brought them in doors was when the Beast from the East struck earlier this year then I shoehorned them into the Conservatory as this was the coldest room in the house as a big change in temperature is too much of a shock for their bodies.