I spotted these while browsing the FB groups and I ordered two to check them out and hopefully use while I was traveling. You vape on your setup and blow the vapour into the system and no vapour should be seen. Unfortunately, they were waiting for me when I got back so I didn't get to test them in real life while traveling... but I have gotten pretty good at Ninja Vaping with my Dvarw DL's... I simply inhale and hold my breath for a few seconds and slowly exhale and little or no vapour comes out. They do work to a degree and they work better with bigger exhales which is nice because that's how you would normally vape... but sadly once you have exhaled a small plume of vapour comes out the mouthpiece. They say it will improve with a bit of use and I will persevere and give my findings once I have used them for a bit. Personally I think it's a bit of a schlep carrying around the little bag with a drip tip on it... let's see how we go!