Sweet! I use the Tenderfeet under my big-box Cary DAC to very good effect.
And speaking of socket savers/lifters, I pulled one of the 6SN7 pieces I got from Suzier apart last night. I was shocked...pleasantly. Solid copper terminals with a direct gold plating for the pin contacts in a full ceramic base. No circuit board with paper-thin socket contacts as many have. For $11.50 with free shipping? Damn. There *is* good stuff available from China.
Note that I would NOT purchase these with the intention of using them as socket savers. The split contacts grip the tube's pins so tightly that this will come out with the tube. Every time. No 'saving' of the amp's socket is gong to occur. But if you need a lifter/riser or something to add some space or clearance, it really doesn't get much better than this.
https://www.ebay.com/itm/1-Octal-8p...306810?hash=item41f612e1ba:g:jQAAAOSwgVJcEMMQ