New Global AC to 9V DC Adapter Compatible with 120 to 9VDC 100mA - 1000mA Outside Diameter OD: 5.5mm x Inner Diameter ID: 2.1mm Tip Center Positive +) - AC to DC Adapter Universal Class 2 transformer work with Bench Scales Scale 9.0V 500mA 0.1A 0.5A - 1A DC9V 1.0A Class 2 Transformer Switching Mode Power Supply Cord Cable Battery Charger Mains PSU ?? (Note: Please Check You Need OD (Outside Diameter): 5.5mm Barrel Round Plug Tip and Center Positive ?. ??NOT Center ? Negative.) ?? Note: The outside diameter is 5.5mm the inside is 2.5mm/2.1mm. ? Center Positive. NOT Center ? Negative. Someone may have bought it by mistake. Please Check For Compatibility With Your Unit. Or Please let us help. Thanks.