Viper RRV PumpViper RRV#258P25: 3 GPM 2500 PSI 3/4" Hollow Shaft Uses 6.5 HP Gas #258P30 3 GPM 3000 PSI 1" Hollow Shaft Using 9 HP Gas #258P35 4 GPM 3500 PSI 1" Hollow Shaft Using 13 HP Gas