Rules:
*You can teleport into and out of it at will
*It has a couple of plug sockets and can connect to internet from the region you teleported in from
*You can take objects and people with you
*As already stated, it is (3m)^3 (3m*3m*3m). The walls are plain plaster with a light in the middle of the ceiling. The pocket dimension is topologically toroidal, so if there weren’t walls and a ceiling/floor (which you can actually destroy) you would loop if you went more than 3m in any direction. Gravity, then, is artificial and can be altered to anywhere from 0 to 2g from a dial on the wall.
Edit: additional specifications
*You can only teleport out to where you teleported in from.
*Time proceeds at the same rate inside the pocket dimension
*There is an eject button for those inside to get out if something happens to you
This is a terrifying power, I gotta say. Like a dude could carry an entire armory around and deploy it Looney-toons-style wherever he wanted.
I would probably just put a bunch of shelves in it and use it as a personal EDC gear storage space. 3m^3 is more than enough space to store pretty much anything you might need in a jiffy.
There’s also apart of me that thinks putting a bed in there would mean not having to bring a date back to your place or to a hotel - but being real I’d probably never use it if I set it up like that.
The thought of having literally every tool conceivable immediately available without having to move is fantastic.
I’m in love with the concept of laying under my car, while also being able to get any particular tool in my hand, without ever having to get up, or having a little pile of sockets, wrenches, and bolts next to me that I have to navigate by feel.