These pumps have advantages of small volumn, light weight, lower noise, long-working time and without repaire. Some types have the automatic device inside. The best features that it can be automatically turmed onoff. When the water level reaches the certain height, it can automatically turned on and discharge water, Or it will be automatically turned off. Application of the pump is much more widely. Whole motor casing is made of plastic, which make the pump have much better insulation performance and delicate appearance.