Rob Kardashian put a ring on it . On Blac Chyna that is. A It was a seven-carat, round-cut brilliant triple excellence diamond as well. He has his friend Ben Baller , founder of IF & Co., to design his fiancée's custom bling. Baller stated "She was really going crazy over the ring. She loves it. $325,000 is pretty close to what he paid" Baller also said how it took him and Rob 5 days to do the ring. He said " He was smiling the whole time.