Title says it all. I loved it when he destroyed feds second serve by returning hella hard in the AO this year... but yah, wandering his set up.
Our frames have a lot in common. We both use the o3/ozone tour, both have tournagrip and we both use rubber bands. i started using my setup before i knew korolev had it lol...
but his strings are definately poly and yellowish.
the possibilities are
Luxilon Big Banger Original
Kirschbaum Touch Turbo
Polyfibre poly hightec
Luxilon Monotec superpoly
heres a pic of him using his racket