As far as I can tell, Lecroy uses them as the OEM for their hv diff probes. I have one sitting on my bench, I'm in the middle of a repair / reverse engineer. I'm headed out of town for the weekend, but maybe I can put up a photo of its guts. It is pretty well made, tons of shielding, good separation. Unfortunately all the chips are obfuscated.. but otherwise, not too bad - plus I got it in non-working condition for $20...