These blankets come in Single bed size and large lap each blanket comes with two covers, one on and one off. Nana's has come to realise there are occasions, such as hospital or pre schools where the blanket may be used by more than one person and daily washing is required. This way you can wash the cover as often as you like. You could do this with the blanket too but the drying time would be longer, with the covers you can put them in the dryer and have them done in no time.