This is a 9V fixed-voltage MyVolts-branded power supply adaptor designed to meet exactly the power specification of your Casio CTK-551 Keyboard. Specifications: - Output voltage is 9V - Max. output amperage is correct for your device - Output tip is the right size and specification - we've tested it thoroughly - 2-pin plug for use with the Type C (EU) wall sockets - Input voltage is AC100-240V, 50/60Hz In addition, this -branded replacement power supply for Casio CTK-551 Keyboard is: - Compliant with all safety standards, and features overvoltage, overcurrent and short-circuit protection to protect your device from damage - RoHS and CE-certified - Energy Star level 6 approved, guaranteeing more efficient delivery of power to your devices, at less cost to you - Covered by a 2 years' warranty: if the power supply fails within 2 years from the date of purchase, we'll replace it, no worries.