Turn the aerator housing counterclockwise and remove it from the faucet. Pull the O-ring off the tip of the faucet spout with your finger. The O-ring prevents leaking between the housing and the faucet. Set the O-ring in a safe place until you are ready to reinstall the housing.
After that, they are referred to as yearlings or stirks if between one and two years of age. A castrated male is called a steer in the United States; older steers are often called bullocks in other parts of the world but in North America this term refers to a young bull.
The female counterpart to a bull is a cow, while a male of the species which has been castrated is a steer, ox or bullock, although in North America this last term refers to a young bull, and in Australia to a draught animal. Usage of these terms varies considerably with area and dialect.