Just received 8 boxes of replacement atty heads plus a knock-off Protank II clearomiser unit. It came with a 2.2 ohm atty and as I always vape with 2.5s I went to swap it out. That's where my problems started. The 2.5 screwed onto the base OK, it just wouldn't/couldn't slide into the centre post in the head. Tried one from each of the boxes and each one was a no-go. The inside diameter of the centre post isn't wide enough to accommodate replacement atties. It might only be a matter of microns but its enough to stop the atties sliding in. So, don't go ordering a bunch these things whatever you do!!

I guess the only mystery is that the 2.2 atty which came with it fitted OK (though I have my suspicions). I've bought a few Protank II clones from them in the past, but this is the first time I've had any issues.