Several friends and I use Synergistic Research duplexes. I prefer the blue, my friends have red and black (earlier/different) duplexes. I know that they consist of commercial/industrial grade and relatively inexpensive outlets. They are processed by SR as they say, with a million volts, either once or repeatedly to linearize the metal materials inside and coat them with a substance that includes graphene. They grip fine. My first SR red duplex KILLED my $40+ hospital grade Hubbles. I gave my friend an SR black duplex to replace a cheap dupex-he was overwhelmed at the difference. I have a relatively higher end system and his is very fine as well. I began my journey into duplexes about a decade ago. Sure, SR duplexes aren't cheap, but in three systems including mine, they are a bargain in sound quality improvement over standard duplexes.
