Although obviously it does not do much, it is actually compatible with a 14mm glass slider like most regular bongs, and if filled with a little amount of water, it will actually percolate, making this a pretty cool party trick! I bent the neck backwards a little to make it more easy to hit.
The keychain hole is 5mm, so if you wish to scale the model down because you just like the looks of it and don't want the functionality, keep that in mind.
Both keychains are actually usable, but what is the difference? with this version, you can only use the keychain with a slider: although a pretty cool trick, you probably won't be going around with a glass piece in your pockets. v2 instead can be used with a normal joint: the hole is much smaller, and the percolation is designed not to raise back into the inline, so you can slide your joint's filter in and it doesn't get wet.
Smoking is really hazardous. Especially from unsafe plastics. That is why I highly recommend you to print this in PETG if you ever think about using it even once, as bacteria has a harder time sticking to it and usually filament brands provide waterproof PETG, which makes it harder for the bad stuff to stick in.