Please take a look at this eBay listing (5951529944). It says these transformers can be used to either step from 110 to 220 or down from 220 to 110. I have been restricted from sending any U.S. electrical appliance (such as a small microwave) to my relatives in Croatia because they use the 220, 50 HZ current. I believe the current there is DC, not sure, so would these even work? Would the HZ difference affect something like a microwave with a simple dial setting? This is way out of my knowing much about so I may not have the questions even properly stated. Please keep any reply in kitchen english.