Sold as a pair, our silicone tube dampers are perfect for reducing microphonic noise in vacuum tubes. Technically, all tubes are microphonic to some degree. We recommend using one per tube on the Op-2 Comp or any older LBA pedals. If you're planning to use them with a 3rd party product, we recommend 2 per tube. Normal rubber o-rings should not be used, as they will break down from the heat of the tubes. Our specially formulated silicone dampers are rated at 400° F (204.4° C). They will not degrade over time. Grab a set of these to push the sonic boundaries of your vacuum tubes!