The weigh-ins (and tomorrow night's fight) are taking place at the MGM Grand Garden Arena in Las Vegas, Nevada. Pacquiao and Mosley will fight at the welterweight (147 lb.) limit, with Pacquiao's WBO welterweight title up for grabs.
Pacquiao is 52-3-2 and the current WBC Super Welterweight World Champion and the WBO Welterweight World Champion. He is the first boxer to win the lineal title in four separate weight classes. He hasn't lost since Erik Morales took a unanimous decision over him in March of 2005, and he obliterated Antonio Margarito over twelve rounds in Cowboys Stadium in November.
Mosley is 46-6-1 with 1 no contest. He drew with Sergio Mora in his last fight in September. He dropped an uncompetitive decision to Floyd Mayweather Jr. in May of 2010, with his last victory coming over Antonio Margarito by TKO in January of 2009.