Vacuum Tube Integrated Amplifier Rated Output: 2.5W×2CH / Compatible Speakers: 4? The vacuum tubes marked with a red circle sticker in the packaging box should be installed on the right side of the unit when facing it. If you have any question or concern, please do not hesitate to contact me. International Buyers - Please Note. We do not mark merchandise values below value or mark items as "gifts" - US and International government regulations prohibit such behavior.