These need no introduction, great inexpensive way to reduce AC line noise. The improvement is not subtle. For use even with regenerators as Paul suggested. They are $495 new retail. Your price is $239 including ground shipping & PayPal in the lower 48 states. As new, mint condition. Buy from someone with 20 years Audiogon history and positive feedback on a 110 transactions under nortonkp user id.
Review: https://www.highfidelityreview.com/ps-audio-noise-harvester.html