I bought one here and one from my local auto parts store to have one for gear lube and one for ATF. The pump is ideal for 1 liter bottles of Mobil gear oil. It was advertised to fit gallon size ATF jugs as well, but unfortunately it's too small to fit around the hole. You can still pump oil/liquid without screwing them in, but you run the risk of contaminating and/or making a mess.