The KBPC608 (BR68) is a four pin single phase bridge rectifier in a black molded case package.

RECTIFIER, 1PH, 6A, 800V THD
No. of Phases: Single
Repetitive Reverse Voltage Vrrm Max: 800V
Forward Current If(AV): 6A
Forward Voltage VF Max: 1.0V
Diode Mounting Type: Through Hole