I recently picked one up. It's not too bad, the voltage drop is MUCH less than I expected. I tested it at a local B&M and it looks like the voltage drop from a brand new Sony VTC4 charged to 4.25 volts is around 0.19 which isn't half bad for a $30.00 mod. I was worried about the k100 style plastic insulator on the spring. So what's a guy to do? Put a 0.15 coil on it and chain vape it for a few minutes. I ran that setup for about thirty minutes taking numerous five second draws until I noticed the battery getting weaker. I disassembled the unit, the battery was slightly warm, but nothing alarming in the slightest. The plastic insulator was completely unscathed. I rebuilt my Stillaire clone with a 24 ga dual coil coming in at 0.50 and have been enjoying the heck out of it ever since.