those definitely store the most but they're not especially stealthy in that you have to pull it out, pull out the bat, load it with a hit, now you have 2 pieces, light it (lighter makes 3) ash the leftovers (not to mention that hot ember on your tongue that I got last night) Pack it up and move on.

Solopipe is at least one piece with a self contained lighter, I can whip that out, take a hit and have it back into my pocket in 10 seconds or less.

But actually I think that the OP was looking for something potentially say Parents can stumble across in a bedroom, test it and move on...

The problem is, any pipe smells like cashed weed.

But the Solopipe is probably the best for stealth semi-public smoking.