This part is a kind of semiconductor called RFC4K.

Function of this product has (RFC2K - RFC4K) HIGH VOLTAGE FAST RECOVERY RECTIFIER.

Manufacturers : CHONGQING PINGYANG ELECTRONICS

Image and pinout :

Some of the text within the PDF file :

CHONG PINGYANG ELECTRONICS CO.,LTD. RFC2K THRU RFC4K HIGH VOLTAGE FAST RECOVERY RECTIFIER VOLTAGE：2000-3000V CURRENT：0.2A FEATURES ·fast switching ·Low leakage ·high current capability ·high surge capability ·High reliability DO-41 1.0(25.4) MIN. .205(5.2) .166(4.2) .034(0.9) .028(0.7) DIA. DIA. MECHANICAL DATA ·Case: Molded plastic ·Epoxy: UL94V-0 rate flame retardant ·Lead: MIL-STD- 202E, Method 208 guaranteed ·Polarity:Color band denotes cathode end ·Mounting position: Any ·Weight: 0.35 grams .107(2.7) .080(2.0) 1.0(25.4) MIN. Dimensions in inches and (millimeters) MAXIMUM RATINGS AND ELECTRONICAL CHARACTERISTICS Ratings at 25℃ ambient temperature unless otherwise specified. Single phase, half wave, 60Hz,resistive or inductive load. For cap [ ... ]

RFC4K PDF Datasheet Download