The ST-xxxW4 series is a servo motor-type high accuracy household voltage stabilizer. Low power consumption. Reliable work. High accuracy of stabilization. Good for use in regions where the net voltage is much fluctuating. ---Input: AC 50v~130v or 160v~250v. Output: AC 220v/110v error 4%. ---With the toroidal core in it. Use servo-motor to regulator the voltage. ---The rated power form 500watts to 5Kwatts. ---With over current protector (fuse protector). ---Within 110v/220v input voltage selector switch. ---With high efficiency at low voltage input. ---Have 6 types cords to choice... ----Certification:CE CQC. ---Warranty: 1 year ---Product list: ST-500W4---47.5*43.5*19cm---4pcs/ctn---20/18kgs ST-1000W4---55.5*45*22cm ---4pcs/ctn---23/21kgs ST-1500W4---49.5*32.5*24.5cm---2pcs/ctn---15/14kgs ST-2000W4---US34.5*30.5*58.5cm---2pcs/ctn---22/20kgs ST-3000W4---34.5*30.5*58.5cm---2pcs/ctn---24/22kgs ST-4000W4---41*30.5*58.5cm---2pcs/ctn---33/31kgs ST-5000W4---41*30.5*58.5cm---2pcs/ctn---36/34kgs If you have interesting, PLS never hesitate and contact us. I will arrange everything for you.