1. Reverse Leakage Current Test Condition: This is the only technical parameter that differs. RGF1G-E3/5CA: `5 µA @ 1700 V` RGF1G-E3/67A: `5 µA @ 400 V` The actual leakage current for both parts at their rated voltage of 400V should be well below 5µA. The E3/5CA's specification at 1700V strongly suggests its die possesses a higher reverse breakdown voltage (BV) margin. This typically results from superior manufacturing processes or more stringent screening, granting it higher reliability at the rated voltage and greater robustness against voltage transients. This directly leads to the second difference. 2. Price: The RGF1G-E3/67A ($0.48) carries a significantly higher price tag than the RGF1G-E3/5CA ($0.22). This price differential primarily reflects the aforementioned die performance margin and potential quality/reliability grade differences. The E3/5CA likely belongs to an "enhanced" or "high-reliability" batch, where the increased BV margin adds to the cost. For consumer electronics, the E3/67A may be sufficient; however, in industrial, automotive, or other high-reliability fields, the extra margin of the E3/5CA can provide tangible value. Summary: Both are the same standard product, but the E3/5CA variant offers a higher voltage margin, likely corresponding to a higher quality grade, which is the main reason for its doubled price. They are interchangeable in non-demanding applications. If the design operates with tight margins or in harsh environments, the E3/5CA with its greater performance headroom is recommended.