The queen and king of racing Muledom are set for another match race May 23 at Los Alamitos Race Course in Southern California.The 11-year-old Black Ruby and her nemesis, 9-year-old Taz, will square off in the $10,000 seventh race at 300 yards. The winner will earn $6,000. Black Ruby will carry 130 pounds and Taz 127 pounds.The "Mule Duel" is scheduled for 9:47 p.m. (PDT), 12:47 a.m. (EDT). The race will be televised live on the TV Games Network as part of the regular coverage from Los Alamitos.Black Ruby and Taz faced each other several times last summer at the Northern California fairs and Del Mar. The Mule races generated a lot of public interest.Black Ruby has won 11 of her last 12 starts, with the lone defeat having come at the hands of Taz."She's pretty fit right now," Black Ruby's trainer, Ron White, told Los Alamitos officials. "We've been schooling her in the gate because that's where she can lose a race."Win wagering will be offered on the Mule Duel. Los Alamitos will also feature racing Mules in the fourth race, a $7,000 event at 350 yards.