Every week the sapphire is being improved, they are working on it nonstop, but becuase this will be a huge project unlike anything we have done before it they will do so in batches, we need to verify how they perform in the real world, with all types of batteries and voltages and juices, each batch we recieve each week will have minor improvements or major ones with minor or major adjustments, They will get them to the point where each ones performs exactly like the last, they are already one of the best performing clearomizer types out there and will get better and better. Dont worry about if you happen to get one that has a issue, we discussed the tight draw causing a burning taste, if this happens to be something you discover with one of the ones you use simply contact us and we will take care of you.