bubbleman was saying the other day that someone was having o-ring blowouts due to pressure formed by the volatility of the terpenes mixed with the rosin because they didn't follow instructions to mix the rosin and terps together and wait 24-36 hours before filling the pen. That seems like an awfully long fill procedure to me. I will reserve judgement until I get the chance to try one but as the terpenes don't ship to the UK,and as I won't try non-canna derived terpenes,I don't see that chance being in the forseeable future. I'd like to think tony and bubbleman have cracked it, although every pen I've ever hit with a concentrate inside has tasted like reclaim after the first couple of hits.