The outside dimensions and design of this line splitter are fine. Both of my clamp -on ammeters fit the 1X and 10X holes well. And, the voltage meter probe holes are handy. But I immediately noticed that , when plugging into the female end, the plugs tended to spring back out.  This was especially true for two blade plugs.  Something was obviously wrong with the female receptacle contacts, so I took the device apart to investigate. Sure enough, the blade contacts were so far recessed into the housing that the plug blades barely made contact.  The internal shape of the plastic housing suggests that it was designed for longer blade contacts, but short ones were used instead. Also, one power wire was not soldered to the blade contact, as were the other wires. The unsoldered wire was simply pushed through a hole in the contact, but someone forgot to solder it. I modified the blade contacts so that plug blades would make good contact, and I soldered the loose wire. Still, however, the female plug receptacle contacts are weak, and will eventually break if this device is used often. To address that problem, I plugged a multi-plug adapter into the female end,  and I plan to tape or glue the adapter into place . That way, the unit's internal weak blade contacts will not repeatedly be stressed by inserting plugs directly into the unit.  Also, the stiff, solid wire inside is soldered to one of the plug receptacle flexible contacts. That joint is bound to eventually break as the receptacle flexes. How this device qualified for a UL listing, I'll never know. But, having spent about two hours modifying it , I do plan to keep it , and use it when needed.  ( The "Kill a Watt" power meters, also sold by Amazon,  are a better bet for most uses, and far more versatile.)