It appears to be a excellent product considering the cost. Very stable output even when source input is fluctuating. Voltage load regulations seems within specs. Efficiency not tested but most likely better when voltage diff is with 5V (step up/down). So far, I have had good experinces with the product. I used it for 5V, 9V, 12V, 24V and 30V applications. S&H was reasonably fast. No issues. Recommend product and Vendor.
Perfect, fast delivery.