Love the idea and the look of this attachment. It definitely does work exactly as expected - be ready to cough like you've never coughed before - though I'm not a huge fan of the nail that comes with it. Easily rectified though as this takes 14mm female nails. Also, you should *definitely* use this with a carb cap. Overall, this thing is freakin' awesome and the price was just right.
Gravity dabs are amazing, just lift slowly before applying your goods to the nail so you don't lose any vapor (I learned that the hard way) 10/10 would buy again